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Wolfgang Meyerhof - One of the best experts on this subject based on the ideXlab platform.
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Taste Receptor function.
Handbook of clinical neurology, 2019Co-Authors: Jonas C. Töle, Maik Behrens, Wolfgang MeyerhofAbstract:Abstract This chapter summarizes the available data about Taste Receptor functions and their role in perception of food with emphasis on the human system. In addition we illuminate the widespread presence of these Receptors throughout the body and discuss some of their extraoral functions. Finally, we describe clinical aspects where Taste Receptor signaling could be relevant.
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The X-ray structure of gurmarin provide new insights into amino acid residues essential for inhibition of the rat sweet Taste Receptor
2018Co-Authors: Maud Sigoillot, Wolfgang Meyerhof, Fabrice Neiers, Anne Brockoff, Nicolas Poirier, Christine Belloir, Pierre Legrand, Christophe Charron, Pierre Roblin, Loïc BriandAbstract:Gurmarin is a polypeptide isolated from the Indian plant Gymnema sylvestre, which specifically suppresses sweet Taste in rodents without affecting responses to other basic Taste stimuli, such as HCl, NaCl, and quinine. Although the exact mechanism of gurmarin inhibition is not known, it has been shown that gurmarin acts via the T1R2/T1R3 sweet Taste Receptor. The gurmarin molecule is made of 35 amino-acid residues and three intramolecular disulfide bridges. We report herein the 1.45 Å X-ray structure of gurmarin heterologously produced using the yeast Pichia pastoris. The structure revealed a typical knottin fold, which is compared with previously reported NMR solution structures. The atomic structure at this resolution allowed us to highlight a flexible region involving hydrophobic amino acid residues previously identified as a putative binding motif for the rat sweet Taste Receptor. By combining cellular based Receptor assay and site-directed mutagenesis of gurmarin, we revealed that several amino acid residues located in this hydrophobic cluster of gurmarin severely affect rat sweet Taste Receptor inhibition. This study demonstrates that gurmarin can be used as a worthwhile tool to decipher the mechanism of sweet Taste inhibition.
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Transsynaptic Tracing from Taste Receptor Cells Reveals Local Taste Receptor Gene Expression in Gustatory Ganglia and Brain
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2015Co-Authors: Anja Voigt, Juliane Bojahr, Masataka Narukawa, Sandra Hübner, Ulrich Boehm, Wolfgang MeyerhofAbstract:Taste perception begins in the oral cavity by interactions of Taste stimuli with specific Receptors. Specific subsets of Taste Receptor cells (TRCs) are activated upon tastant stimulation and transmit Taste signals to afferent nerve fibers and ultimately to the brain. How specific TRCs impinge on the innervating nerves and how the activation of a subset of TRCs leads to the discrimination of tastants of different qualities and intensities is incompletely understood. To investigate the organization of Taste circuits, we used gene targeting to express the transsynaptic tracer barley lectin (BL) in the gustatory system of mice. Because TRCs are not synaptically connected with the afferent nerve fibers, we first analyzed tracer production and transfer within the Taste buds (TBs). Surprisingly, we found that BL is laterally transferred across all cell types in TBs of mice expressing the tracer under control of the endogenous Tas1r1 and Tas2r131 promotor, respectively. Furthermore, although we detected the BL tracer in both ganglia and brain, we also found local low-level Tas1r1 and Tas2r131 gene, and thus tracer expression in these tissues. Finally, we identified the Tas1r1 and Tas2r131-expressing cells in the peripheral and CNS using a binary genetic approach. Together, our data demonstrate that genetic transsynaptic tracing from bitter and umami Receptor cells does not selectively label Taste-specific neuronal circuits and reveal local Taste Receptor gene expression in the gustatory ganglia and the brain. SIGNIFICANCE STATEMENT Previous papers described the organization of Taste pathways in mice expressing a transsynaptic tracer from transgenes in bitter or sweet/umami-sensing Taste Receptor cells. However, reported results differ dramatically regarding the numbers of synapses crossed and the reduction of signal intensity after each transfer step. Nevertheless, all groups claimed this approach appropriate for quality-specific visualization of Taste pathways. In the present study, we demonstrate that genetic transsynaptic tracing originating from umami and bitter Taste Receptor cells does not selectively label Taste quality-specific neuronal circuits due to lateral transfer of the tracer in the Taste bud and Taste Receptor expression in sensory ganglia and brain. Moreover, we visualized for the first time Taste Receptor-expressing cells in the PNS and CNS.
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Taste Receptor gene expression outside the gustatory system
2014Co-Authors: Maik Behrens, Simone Prandi, Wolfgang MeyerhofAbstract:The sense of Taste facilitates the recognition of beneficial or potentially harmful food constituents prior to ingestion. For the detection of tastants, epithelial specializations in the oral cavity are equipped with Taste Receptor molecules that interact with sweet, umami (the Taste of l-amino acids), salty, sour, and bitter-tasting substances. Over the past years, numerous tissues in addition to gustatory sensory tissue have been identified to express Taste Receptor molecules. These findings bear important implications for the roles Taste Receptors fulfill in vertebrates, which are currently envisioned much broader than thought previously. Taste receptive molecules are present in the brain, respiratory and gastrointestinal tracts, heart, male reproductive tissue, as well as other areas of the body just beginning to emerge. This review summarizes current knowledge on the occurrence and functional implications of Taste receptive molecules outside the oral cavity.
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Taste responses in mice lacking Taste Receptor subunit t1r1
The Journal of Physiology, 2013Co-Authors: Yoko Kusuhara, Wolfgang Meyerhof, Ryusuke Yoshida, Anja Voigt, Sandra Hübner, Ulrich Boehm, Tadahiro Ohkuri, Keiko Yasumatsu, Katsumasa Maeda, Yuzo NinomiyaAbstract:Key points • The Taste Receptor heterodimer T1R1 + T1R3, metabotropic glutamate Receptors (mGluRs) and/or their variants may function as umami Taste Receptors. • Here, we used newly developed T1R1−/− mice and examined the role of T1R1 and mGluRs in Taste detection. • The T1R1−/− mice exhibited seriously diminished synergistic responses to glutamate and inosine monophosphate but not to glutamate alone and significantly smaller responses to sweeteners. • Addition of mGluR antagonists significantly inhibited responses to glutamate in both T1R1−/− and heterozygous T1R1+/− mice. • Taken together, these results suggest that T1R1 mainly contributes to umami Taste synergism and partly to sweet sensitivity, while mGluRs are involved in the detection of umami compounds. Abstract The T1R1 Receptor subunit acts as an umami Taste Receptor in combination with its partner, T1R3. In addition, metabotropic glutamate Receptors (brain and Taste variants of mGluR1 and mGluR4) are thought to function as umami Taste Receptors. To elucidate the function of T1R1 and the contribution of mGluRs to umami Taste detection in vivo, we used newly developed knock-out (T1R1−/−) mice, which lack the entire coding region of the Tas1r1 gene and express mCherry in T1R1-expressing cells. Gustatory nerve recordings demonstrated that T1R1−/− mice exhibited a serious deficit in inosine monophosphate-elicited synergy but substantial residual responses to glutamate alone in both chorda tympani and glossopharyngeal nerves. Interestingly, chorda tympani nerve responses to sweeteners were smaller in T1R1−/− mice. Taste cell recordings demonstrated that many mCherry-expressing Taste cells in T1R1+/− mice responded to sweet and umami compounds, whereas those in T1R1−/− mice responded to sweet stimuli. The proportion of sweet-responsive cells was smaller in T1R1−/− than in T1R1+/− mice. Single-cell RT-PCR demonstrated that some single mCherry-expressing cells expressed all three T1R subunits. Chorda tympani and glossopharyngeal nerve responses to glutamate were significantly inhibited by addition of mGluR antagonists in both T1R1−/− and T1R1+/− mice. Conditioned Taste aversion tests demonstrated that both T1R1−/− and T1R1+/− mice were equally capable of discriminating glutamate from other basic Taste stimuli. Avoidance conditioned to glutamate was significantly reduced by addition of mGluR antagonists. These results suggest that T1R1-expressing cells mainly contribute to umami Taste synergism and partly to sweet sensitivity and that mGluRs are involved in the detection of umami compounds.
Yuzo Ninomiya - One of the best experts on this subject based on the ideXlab platform.
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Intracellular acidification is required for full activation of the sweet Taste Receptor by miraculin.
Scientific reports, 2016Co-Authors: Keisuke Sanematsu, Noriatsu Shigemura, Ryusuke Yoshida, Masayuki Kitagawa, Satoru Nirasawa, Yuzo NinomiyaAbstract:Acidification of the glycoprotein, miraculin (MCL), induces sweet Taste in humans, but not in mice. The sweet Taste induced by MCL is more intense when acidification occurs with weak acids as opposed to strong acids. MCL interacts with the human sweet Receptor subunit hTAS1R2, but the mechanisms by which the acidification of MCL activates the sweet Taste Receptor remain largely unexplored. The work reported here speaks directly to this activation by utilizing a sweet Receptor TAS1R2 + TAS1R3 assay. In accordance with previous data, MCL-applied cells displayed a pH dependence with citric acid (weak acid) being right shifted to that with hydrochloric acid (strong acid). When histidine residues in both the intracellular and extracellular region of hTAS1R2 were exchanged for alanine, Taste-modifying effect of MCL was reduced or abolished. Stronger intracellular acidification of HEK293 cells was induced by citric acid than by HCl and Taste-modifying effect of MCL was proportional to intracellular pH regardless of types of acids. These results suggest that intracellular acidity is required for full activation of the sweet Taste Receptor by MCL.
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multimodal function of the sweet Taste Receptor expressed in pancreatic β cells generation of diverse patterns of intracellular signals by sweet agonists
Endocrine Journal, 2013Co-Authors: Yuko Nakagawa, Masahiro Nagasawa, Hideo Mogami, Martin J Lohse, Yuzo Ninomiya, Itaru KojimaAbstract:: The sweet Taste Receptor is expressed in the Taste bud and is activated by numerous sweet molecules with diverse chemical structures. It is, however, not known whether these sweet agonists induce a similar cellular response in target cells. Using MIN6 cells, a pancreatic β-cell line expressing endogenous sweet Taste Receptor, we addressed this question by monitoring changes in cytoplasmic Ca2+ ([Ca2+]i) and cAMP ([cAMP]i) induced by four sweet Taste Receptor agonists. Glycyrrhizin evoked sustained elevation of [Ca2+]i but [cAMP]i was not affected. Conversely, an artificial sweetener saccharin induced sustained elevation of [cAMP]i but did not increase [Ca2+]i. In contrast, sucralose and acesulfame K induced rapid and sustained increases in both [Ca2+]i and [cAMP]i. Although the latter two sweeteners increased [Ca2+]i and [cAMP]i, their actions were not identical: [Ca2+]i response to sucralose but not acesulfame K was inhibited by gurmarin, an antagonist of the sweet Taste Receptor which blocks the gustducin-dependent pathway. In addition, [Ca2+]i response to acesulfame K but not to sucralose was resistant to a Gq inhibitor. These results indicate that four types of sweeteners activate the sweet Taste Receptor differently and generate distinct patterns of intracellular signals. The sweet Taste Receptor has amazing multimodal functions producing multiple patterns of intracellular signals.
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Taste responses in mice lacking Taste Receptor subunit t1r1
The Journal of Physiology, 2013Co-Authors: Yoko Kusuhara, Wolfgang Meyerhof, Ryusuke Yoshida, Anja Voigt, Sandra Hübner, Ulrich Boehm, Tadahiro Ohkuri, Keiko Yasumatsu, Katsumasa Maeda, Yuzo NinomiyaAbstract:Key points • The Taste Receptor heterodimer T1R1 + T1R3, metabotropic glutamate Receptors (mGluRs) and/or their variants may function as umami Taste Receptors. • Here, we used newly developed T1R1−/− mice and examined the role of T1R1 and mGluRs in Taste detection. • The T1R1−/− mice exhibited seriously diminished synergistic responses to glutamate and inosine monophosphate but not to glutamate alone and significantly smaller responses to sweeteners. • Addition of mGluR antagonists significantly inhibited responses to glutamate in both T1R1−/− and heterozygous T1R1+/− mice. • Taken together, these results suggest that T1R1 mainly contributes to umami Taste synergism and partly to sweet sensitivity, while mGluRs are involved in the detection of umami compounds. Abstract The T1R1 Receptor subunit acts as an umami Taste Receptor in combination with its partner, T1R3. In addition, metabotropic glutamate Receptors (brain and Taste variants of mGluR1 and mGluR4) are thought to function as umami Taste Receptors. To elucidate the function of T1R1 and the contribution of mGluRs to umami Taste detection in vivo, we used newly developed knock-out (T1R1−/−) mice, which lack the entire coding region of the Tas1r1 gene and express mCherry in T1R1-expressing cells. Gustatory nerve recordings demonstrated that T1R1−/− mice exhibited a serious deficit in inosine monophosphate-elicited synergy but substantial residual responses to glutamate alone in both chorda tympani and glossopharyngeal nerves. Interestingly, chorda tympani nerve responses to sweeteners were smaller in T1R1−/− mice. Taste cell recordings demonstrated that many mCherry-expressing Taste cells in T1R1+/− mice responded to sweet and umami compounds, whereas those in T1R1−/− mice responded to sweet stimuli. The proportion of sweet-responsive cells was smaller in T1R1−/− than in T1R1+/− mice. Single-cell RT-PCR demonstrated that some single mCherry-expressing cells expressed all three T1R subunits. Chorda tympani and glossopharyngeal nerve responses to glutamate were significantly inhibited by addition of mGluR antagonists in both T1R1−/− and T1R1+/− mice. Conditioned Taste aversion tests demonstrated that both T1R1−/− and T1R1+/− mice were equally capable of discriminating glutamate from other basic Taste stimuli. Avoidance conditioned to glutamate was significantly reduced by addition of mGluR antagonists. These results suggest that T1R1-expressing cells mainly contribute to umami Taste synergism and partly to sweet sensitivity and that mGluRs are involved in the detection of umami compounds.
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Modulation of sweet responses of Taste Receptor cells
Seminars in cell & developmental biology, 2012Co-Authors: Ryusuke Yoshida, Keisuke Sanematsu, Noriatsu Shigemura, Mayu Niki, Masafumi Jyotaki, Yuzo NinomiyaAbstract:Taste Receptor cells play a major role in detection of chemical compounds in the oral cavity. Information derived from Taste Receptor cells, such as sweet, bitter, salty, sour and umami is important for evaluating the quality of food components. Among five basic Taste qualities, sweet Taste is very attractive for animals and influences food intake. Recent studies have demonstrated that sweet Taste sensitivity in Taste Receptor cells would be affected by leptin and endocannabinoids. Leptin is an anorexigenic mediator that reduces food intake by acting on leptin Receptor Ob-Rb in the hypothalamus. Endocannabinoids such as anandamide [N-arachidonoylethanolamine (AEA)] and 2-arachidonoyl glycerol (2-AG) are known as orexigenic mediators that act via cannabinoid Receptor 1 (CB1) in the hypothalamus and limbic forebrain to induce appetite and stimulate food intake. At the peripheral gustatory organs, leptin selectively suppresses and endocannabinoids selectively enhance sweet Taste sensitivity via Ob-Rb and CB1 expressed in sweet sensitive Taste cells. Thus leptin and endocannabinoids not only regulate food intake via central nervous systems but also modulate palatability of foods by altering peripheral sweet Taste responses. Such reciprocal modulation of leptin and endocannabinoids on peripheral sweet sensitivity may play an important role in regulating energy homeostasis.
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sweet Taste Receptor expressed in pancreatic β cells activates the calcium and cyclic amp signaling systems and stimulates insulin secretion
PLOS ONE, 2009Co-Authors: Yuko Nakagawa, Noriatsu Shigemura, Masahiro Nagasawa, Hideo Mogami, Martin J Lohse, Yuzo Ninomiya, Satoko Yamada, Akemi Hara, Viacheslav O Nikolaev, Itaru KojimaAbstract:Background Sweet Taste Receptor is expressed in the Taste buds and enteroendocrine cells acting as a sugar sensor. We investigated the expression and function of the sweet Taste Receptor in MIN6 cells and mouse islets. Methodology/Principal Findings The expression of the sweet Taste Receptor was determined by RT–PCR and immunohistochemistry. Changes in cytoplasmic Ca2+ ([Ca2+]c) and cAMP ([cAMP]c) were monitored in MIN6 cells using fura-2 and Epac1-camps. Activation of protein kinase C was monitored by measuring translocation of MARCKS-GFP. Insulin was measured by radioimmunoassay. mRNA for T1R2, T1R3, and gustducin was expressed in MIN6 cells. In these cells, artificial sweeteners such as sucralose, succharin, and acesulfame-K increased insulin secretion and augmented secretion induced by glucose. Sucralose increased biphasic increase in [Ca2+]c. The second sustained phase was blocked by removal of extracellular calcium and addition of nifedipine. An inhibitor of inositol(1, 4, 5)-trisphophate Receptor, 2-aminoethoxydiphenyl borate, blocked both phases of [Ca2+]c response. The effect of sucralose on [Ca2+]c was inhibited by gurmarin, an inhibitor of the sweet Taste Receptor, but not affected by a Gq inhibitor. Sucralose also induced sustained elevation of [cAMP]c, which was only partially inhibited by removal of extracellular calcium and nifedipine. Finally, mouse islets expressed T1R2 and T1R3, and artificial sweeteners stimulated insulin secretion. Conclusions Sweet Taste Receptor is expressed in β-cells, and activation of this Receptor induces insulin secretion by Ca2+ and cAMP-dependent mechanisms.
Loïc Briand - One of the best experts on this subject based on the ideXlab platform.
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The X-ray structure of gurmarin provide new insights into amino acid residues essential for inhibition of the rat sweet Taste Receptor
2018Co-Authors: Maud Sigoillot, Wolfgang Meyerhof, Fabrice Neiers, Anne Brockoff, Nicolas Poirier, Christine Belloir, Pierre Legrand, Christophe Charron, Pierre Roblin, Loïc BriandAbstract:Gurmarin is a polypeptide isolated from the Indian plant Gymnema sylvestre, which specifically suppresses sweet Taste in rodents without affecting responses to other basic Taste stimuli, such as HCl, NaCl, and quinine. Although the exact mechanism of gurmarin inhibition is not known, it has been shown that gurmarin acts via the T1R2/T1R3 sweet Taste Receptor. The gurmarin molecule is made of 35 amino-acid residues and three intramolecular disulfide bridges. We report herein the 1.45 Å X-ray structure of gurmarin heterologously produced using the yeast Pichia pastoris. The structure revealed a typical knottin fold, which is compared with previously reported NMR solution structures. The atomic structure at this resolution allowed us to highlight a flexible region involving hydrophobic amino acid residues previously identified as a putative binding motif for the rat sweet Taste Receptor. By combining cellular based Receptor assay and site-directed mutagenesis of gurmarin, we revealed that several amino acid residues located in this hydrophobic cluster of gurmarin severely affect rat sweet Taste Receptor inhibition. This study demonstrates that gurmarin can be used as a worthwhile tool to decipher the mechanism of sweet Taste inhibition.
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Characterization of ligands for the human T1R2 sweet Taste Receptor (obtention "Manfred Rothe Poster Award")
2016Co-Authors: Anni Laffitte, Fabrice Neiers, Loïc BriandAbstract:The human sweet-Taste Receptor is a heterodimer composed of two class C G-protein coupled Receptors (GPCR), T1R2 and T1R3. Both subunits possess a large N-terminal domain (NTD) linked to a heptahelical transmembrane domain (TM) by a cysteine rich domain (CRD) [1]. Cellular assays, molecular docking and mutagenesis studies have revealed that small sweet ligands interact primarily with the NTD of T1R2 (T1R2-NTD) [2, 3]. To further elucidate the contribution of T1R2-NTD to small sweet ligand binding, we overexpressed T1R2-NTD in Escherichia coli as inclusion bodies [4, 5]. Human T1R2-NTD was refolded and the correct formation of secondary structures was verified using circular dichroism. T1R2-NTD was then characterized for its ability to interact with a number of known sweet tasting ligands using intrinsic tryptophan fluorescence. We found the measured affinities with the wild-type T1R2-NTD are in agreement with cellular based assays conducted on the full-length Receptor and sensory analysis in humans. Using site-directed mutagenesis, we confirmed the binding site of sucralose. This strategy will be used to study the binding mechanism of other sweeteners including sweet-tasting proteins, such as brazzein and monellin. 1.Nelson, G., et al., Mammalian sweet Taste Receptors. Cell, 2001. 106(3): p. 381-90. 2.Masuda, K., et al., Characterization of the modes of binding between human sweet Taste Receptor and low-molecular-weight sweet compounds. PLoS One, 2012. 7(4): p. e35380. 3.Xu, H., et al., Different functional roles of T1R subunits in the heteromeric Taste Receptors. Proc Natl Acad Sci U S A, 2004. 101(39): p. 14258-63. 4.Maitrepierre, E., et al., Recombinant expression, in vitro refolding, and biophysical characterization of the N-terminal domain of T1R3 Taste Receptor. Protein Expr Purif, 2012. 83(1): p. 75-83. 5.Nie, Y., et al., Distinct contributions of T1R2 and T1R3 Taste Receptor subunits to the detection of sweet stimuli. Curr Biol, 2005. 15(21): p. 1948-52.
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Functional roles of the sweet Taste Receptor in oral and extraoral tissues
Current Opinion in Clinical Nutrition and Metabolic Care, 2014Co-Authors: Anni Laffitte, Fabrice Neiers, Loïc BriandAbstract:Purpose of review: This review summarizes and discusses the current knowledge about the physiological roles of the sweet Taste Receptor in oral and extraoral tissues. Recent findings: The expression of a functional sweet Taste Receptor has been reported in numerous extragustatory tissues, including the gut, pancreas, bladder, brain and, more recently, bone and adipose tissues. In the gut, this Receptor has been suggested to be involved in luminal glucose sensing, the release of some satiety hormones, the expression of glucose transporters, and the maintenance of glucose homeostasis. More recently, the sweet Taste Receptor was proposed to regulate adipogenesis and bone biology. Summary: The perception of sweet Taste is mediated by the T1R2/T1R3 Receptor, which is expressed in the oral cavity, wherein it provides input on the caloric and macronutrient contents of ingested food. This Receptor recognizes all the chemically diverse compounds perceived as sweet by human beings, including natural sugars and sweeteners. Importantly, the expression of a functional sweet Taste Receptor has been reported in numerous extragustatory tissues, wherein it has been proposed to regulate metabolic processes. This newly recognized role of the sweet Taste Receptor makes this Receptor a potential novel therapeutic target for the treatment of obesity and related metabolic dysfunctions, such as diabetes and hyperlipidemia.
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Functional roles of the sweet Taste Receptor in oral and extraoral tissues.
Current opinion in clinical nutrition and metabolic care, 2014Co-Authors: Anni Laffitte, Fabrice Neiers, Loïc BriandAbstract:Purpose of review This review summarizes and discusses the current knowledge about the physiological roles of the sweet Taste Receptor in oral and extraoral tissues.
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Expression and biophysical characterization of the human T1R1 Taste Receptor subunit
2011Co-Authors: Maud Sigoillot, Laurence Le Pessot, Loïc BriandAbstract:Expression and biophysical characterization of the human T1R1 Taste Receptor subunit. 21. Congress of the european chemoreception research organisation (ECRO)
Marcel Winnig - One of the best experts on this subject based on the ideXlab platform.
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sweet Taste Receptor interacting protein cib1 is a general inhibitor of insp3 dependent ca2 release in vivo
Journal of Neurochemistry, 2008Co-Authors: Jan K Hennigs, Nicole Burhenne, Frauke Stähler, Marcel Winnig, Bettina Walter, Wolfgang Meyerhof, Hartwig SchmaleAbstract:In a search for sweet Taste Receptor interacting proteins, we have identified the calcium- and integrin-binding protein 1 (CIB1) as specific binding partner of the intracellular carboxyterminal domain of the rat sweet Taste Receptor subunit Tas1r2. In heterologous human embryonic kidney 293 (HEK293) cells, the G protein chimeras Gα16gust44 and Gα15i3 link the sweet Taste Receptor dimer TAS1R2/TAS1R3 to an inositol 1,4,5-trisphosphate (InsP3)-dependent Ca2+ release pathway. To demonstrate the influence of CIB1 on the cytosolic Ca2+ concentration, we used sweet and umami compounds as well as other InsP3-generating ligands in FURA-2-based Ca2+ assays in wild-type HEK293 cells and HEK293 cells expressing functional human sweet and umami Taste Receptor dimers. Stable and transient depletion of CIB1 by short-hairpin RNA increased the Ca2+ response of HEK293 cells to the InsP3-generating ligands ATP, UTP and carbachol. Over-expression of CIB1 had the opposite effect as shown for the sweet ligand saccharin, the umami Receptor ligand monosodium glutamate and UTP. The CIB1 effect was dependent on the thapsigargin-sensitive Ca2+ store of the endoplasmic reticulum (ER) and independent of extracellular Ca2+. The function of CIB1 on InsP3-evoked Ca2+ release from the ER is most likely mediated by its interaction with the InsP3 Receptor. Thus, CIB1 seems to be an inhibitor of InsP3-dependent Ca2+ release in vivo.
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sweet Taste Receptor interacting protein cib1 is a general inhibitor of insp3 dependent ca2 release in vivo
Journal of Neurochemistry, 2008Co-Authors: Jan K Hennigs, Nicole Burhenne, Frauke Stähler, Marcel Winnig, Bettina Walter, Wolfgang Meyerhof, Hartwig SchmaleAbstract:In a search for sweet Taste Receptor interacting proteins, we have identified the calcium- and integrin-binding protein 1 (CIB1) as specific binding partner of the intracellular carboxyterminal domain of the rat sweet Taste Receptor subunit Tas1r2. In heterologous human embryonic kidney 293 (HEK293) cells, the G protein chimeras Gα16gust44 and Gα15i3 link the sweet Taste Receptor dimer TAS1R2/TAS1R3 to an inositol 1,4,5-trisphosphate (InsP3)-dependent Ca2+ release pathway. To demonstrate the influence of CIB1 on the cytosolic Ca2+ concentration, we used sweet and umami compounds as well as other InsP3-generating ligands in FURA-2-based Ca2+ assays in wild-type HEK293 cells and HEK293 cells expressing functional human sweet and umami Taste Receptor dimers. Stable and transient depletion of CIB1 by short-hairpin RNA increased the Ca2+ response of HEK293 cells to the InsP3-generating ligands ATP, UTP and carbachol. Over-expression of CIB1 had the opposite effect as shown for the sweet ligand saccharin, the umami Receptor ligand monosodium glutamate and UTP. The CIB1 effect was dependent on the thapsigargin-sensitive Ca2+ store of the endoplasmic reticulum (ER) and independent of extracellular Ca2+. The function of CIB1 on InsP3-evoked Ca2+ release from the ER is most likely mediated by its interaction with the InsP3 Receptor. Thus, CIB1 seems to be an inhibitor of InsP3-dependent Ca2+ release in vivo.
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the binding site for neohesperidin dihydrochalcone at the human sweet Taste Receptor
BMC Structural Biology, 2007Co-Authors: Marcel Winnig, Bernd Bufe, Jay Patrick Slack, Nicole A Kratochwil, Wolfgang MeyerhofAbstract:Background Differences in sweet Taste perception among species depend on structural variations of the sweet Taste Receptor. The commercially used isovanillyl sweetener neohesperidin dihydrochalcone activates the human but not the rat sweet Receptor TAS1R2+TAS1R3. Analysis of interspecies combinations and chimeras of rat and human TAS1R2+TAS1R3 suggested that the heptahelical domain of human TAS1R3 is crucial for the activation of the sweet Receptor by neohesperidin dihydrochalcone.
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Valine 738 and lysine 735 in the fifth transmembrane domain of rTas1r3 mediate insensitivity towards lactisole of the rat sweet Taste Receptor
BMC Neuroscience, 2005Co-Authors: Marcel Winnig, Bernd Bufe, Wolfgang MeyerhofAbstract:Background The sweet Taste inhibitor lactisole acts on the human sweet Taste Receptor heteromer TAS1R2-TAS1R3 but not on its rodent counterpart. Recently, it was shown that the lactisole sensitivity of the human sweet Taste Receptor involves the part of TAS1R3 encompassing the seven transmembrane regions but not the huge N-terminal domain. Using mutational analysis we investigated which amino acid residues distinguish lactisole insensitive rat from sensitive human T1R3 Receptors.
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Valine 738 and lysine 735 in the fifth transmembrane domain of rTas1r3 mediate insensitivity towards lactisole of the rat sweet Taste Receptor
BMC Neuroscience, 2005Co-Authors: Marcel Winnig, Bernd Bufe, Wolfgang MeyerhofAbstract:Background The sweet Taste inhibitor lactisole acts on the human sweet Taste Receptor heteromer TAS1R2-TAS1R3 but not on its rodent counterpart. Recently, it was shown that the lactisole sensitivity of the human sweet Taste Receptor involves the part of TAS1R3 encompassing the seven transmembrane regions but not the huge N-terminal domain. Using mutational analysis we investigated which amino acid residues distinguish lactisole insensitive rat from sensitive human T1R3 Receptors. Results The functional analysis of specific Receptor mutants in HEK293T cells revealed that the exchange of valine 738 in the fifth transmembrane domain of rTas1r3 by an alanine is sufficient to confer lactisole sensitivity to the rat sweet Taste Receptor. The sensitivity of this Receptor mutant is ~2 fold lower than the sensitivity of the human sweet Taste Receptor. Additional substitution of lysine 735 by phenylalanine in rTas1r3 results in a rat sweet Taste Receptor that is as sensitive to lactisole as its human counterpart. The exchange of valine 738 to alanine was accompanied by a ~50% reduction in Receptor efficacy. This effect was seen with all six different sweet compounds examined. Conclusion The lactisole insensitivity of rat sweet Taste Receptor is caused by only two amino acids in transmembrane region five, which is critical for the interaction of lactisole with the sweet Taste Receptor. The observation that the mutant Receptor simultaneously displays a generally reduced sensitivity towards all agonists suggests that the lactisole insensitivity of the rodent Receptor might be more likely caused by the inaccessibility of the lactisole binding site rather then by its direct disruption.
John A. Desimone - One of the best experts on this subject based on the ideXlab platform.
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Changes in Taste Receptor cell [Ca2+]i modulate chorda tympani responses to bitter, sweet, and umami Taste stimuli
Journal of Neurophysiology, 2012Co-Authors: John A. Desimone, Tam-hao T. Phan, Zuojun Ren, Shobha Mummalaneni, Vijay LyallAbstract:The relationship between Taste Receptor cell (TRC) intracellular Ca2+ ([Ca2+]i) and rat chorda tympani (CT) nerve responses to bitter (quinine and denatonium), sweet (sucrose, glycine, and erythrit...
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A novel vanilloid Receptor-1 (VR-1) variant mammalian salt Taste Receptor.
Chemical Senses, 2005Co-Authors: Vijay Lyall, Tam-hao T. Phan, Gerard L. Heck, Anna K. Vinnikova, Shobha Ghosh, John A. DesimoneAbstract:An amiloride-insensitive (AI) salt Taste Receptor is the predominant transducer of Na+ Taste in some mammalian species. Accordingly, the objective of this study was to characterize the AI-salt Taste Receptor. The AI-salt Taste Receptor in rat and mouse fungiform Taste Receptor cells (TRCs) was activated by the vanilloid Receptor-1 (VR-1) agonists, resiniferatoxin (RTX), capsiacin (CAP) and elevated temperature (>38°), and was inhibited by the VR-1 antagonist, SB-366791 (Lyall et al., 2004). VR-1 knockout mice demonstrated no functional AI-salt Taste Receptor and no salt sensitivity to vanilloids and temperature. We conclude that the AI-salt Taste Receptor is derived from the VR-1 gene.
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the mammalian amiloride insensitive non specific salt Taste Receptor is a vanilloid Receptor 1 variant
The Journal of Physiology, 2004Co-Authors: Vijay Lyall, Tam-hao T. Phan, Gerard L. Heck, Anna K. Vinnikova, Shobha Ghosh, Rammy I Alam, Oneal F Russell, Shahbaz A Malik, John W Bigbee, John A. DesimoneAbstract:The amiloride-insensitive salt Taste Receptor is the predominant transducer of salt Taste in some mammalian species, including humans. The physiological, pharmacological and biochemical properties of the amiloride-insensitive salt Taste Receptor were investigated by RT-PCR, by the measurement of unilateral apical Na+ fluxes in polarized rat fungiform Taste Receptor cells and by chorda tympani Taste nerve recordings. The chorda tympani responses to NaCl, KCl, NH4Cl and CaCl2 were recorded in Sprague-Dawley rats, and in wild-type and vanilloid Receptor-1 (VR-1) knockout mice. The chorda tympani responses to mineral salts were monitored in the presence of vanilloids (resiniferatoxin and capsaicin), VR-1 antagonists (capsazepine and SB-366791), and at elevated temperatures. The results indicate that the amiloride-insensitive salt Taste Receptor is a constitutively active non-selective cation channel derived from the VR-1 gene. It accounts for all of the amiloride-insensitive chorda tympani Taste nerve response to Na+ salts and part of the response to K+, NH4+ and Ca2+ salts. It is activated by vanilloids and temperature (> 38°C), and is inhibited by VR-1 antagonists. In the presence of vanilloids, external pH and ATP lower the temperature threshold of the channel. This allows for increased salt Taste sensitivity without an increase in temperature. VR-1 knockout mice demonstrate no functional amiloride-insensitive salt Taste Receptor and no salt Taste sensitivity to vanilloids and temperature. We conclude that the mammalian non-specific salt Taste Receptor is a VR-1 variant.
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Effects of osmolarity on Taste Receptor cell size and function.
The American journal of physiology, 1999Co-Authors: Vijay Lyall, John A. Desimone, Gerard L. Heck, George M. FeldmanAbstract:Osmotic effects on salt Taste were studied by recording from the rat chorda tympani (CT) nerve and by measuring changes in cell volume of isolated rat fungiform Taste Receptor cells (TRCs). Mannito...
