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Yu Y, Liu S, Zhang X, Yu W, Pei X, Liu L, Jin Y. Identification and prediction of milk-derived bitter taste peptides based on peptidomics technology and machine learning method. Food Chem 2024; 433:137288. [PMID: 37683467 DOI: 10.1016/j.foodchem.2023.137288] [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: 04/26/2023] [Revised: 07/19/2023] [Accepted: 08/24/2023] [Indexed: 09/10/2023]
Abstract
Bitter taste peptides (BPs) are vital for drug and nutrition research, but large-scale screening of them is still time-consuming and costly. This study developed a complete workflow for screening BPs based on peptidomics technology and machine learning method. Using an expanded dataset and a new combination of BPs' characteristic factors, a novel classification prediction model (CPM-BP) based on the Light Gradient Boosting Machine algorithm was constructed with an accuracy of 90.3 % for predicting BPs. Among 724 significantly different peptides between spoiled and fresh UHT milk, 180 potential BPs were predicted using CPM-BP and eleven of them were previously reported. One known BP (FALPQYLK) and three predicted potential BPs (FALPQYL, FFVAPFPEVFGKE, EMPFPKYP) were verified by determination of calcium mobilization of HEK293T cells expressing human bitter taste receptor T2R4 (hT2R4). Three potential BPs could activate the hT2R4 and are demonstrated to be BPs, which proved the effectiveness of CPM-BP.
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Affiliation(s)
- Yang Yu
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China
| | - Shengchi Liu
- School of Information Science and Engineering, Dalian Polytechnic University, Dalian, Liaoning 116034, China
| | - Xinchen Zhang
- School of Information Science and Engineering, Dalian Polytechnic University, Dalian, Liaoning 116034, China
| | - Wenhao Yu
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China
| | - Xiaoyan Pei
- Inner Mongolia Yili Industrial Group Co., Ltd., Hohhot, Inner Mongolia 010110, China
| | - Li Liu
- School of Information Science and Engineering, Dalian Polytechnic University, Dalian, Liaoning 116034, China.
| | - Yan Jin
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China.
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2
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Bloxham CJ, Hulme KD, Fierro F, Fercher C, Pegg CL, O'Brien SL, Foster SR, Short KR, Furness SGB, Reichelt ME, Niv MY, Thomas WG. Cardiac human bitter taste receptors contain naturally occurring variants that alter function. Biochem Pharmacol 2024; 219:115932. [PMID: 37989413 DOI: 10.1016/j.bcp.2023.115932] [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: 07/13/2023] [Revised: 10/26/2023] [Accepted: 11/16/2023] [Indexed: 11/23/2023]
Abstract
Bitter taste receptors (T2R) are a subfamily of G protein-coupled receptors that enable humans to detect aversive and toxic substances. The ability to discern bitter compounds varies between individuals and is attributed mainly to naturally occurring T2R polymorphisms. T2Rs are also expressed in numerous non-gustatory tissues, including the heart, indicating potential contributions to cardiovascular physiology. In this study. T2Rs that have previously been identified in human cardiac tissues (T2Rs - 10, 14, 30, 31, 46 and 50) and their naturally occurring polymorphisms were functionally characterised. The ligand-dependent signaling responses of some T2R variants were completely abolished (T2R30 Leu252 and T2R46 Met228), whereas other receptor variants had moderate changes in their maximal response, but not potency, relative to wild type. Using a cAMP fluorescent biosensor, we reveal the productive coupling of T2R14, but not the T2R14 Phe201 variant, to endogenous Gαi. Modeling revealed that these variants resulted in altered interactions that generally affected ligand binding (T2R30 Leu252) or Gα protein interactions (T2R46 Met228 and T2R14 Phe201), rather than receptor structural stability. Interestingly, this study is the first to show a difference in signaling for T2R50 Tyr203 (rs1376251) which has been associated with cardiovascular disease. The observation of naturally occurring functional variation in the T2Rs with the greatest expression in the heart is important, as their discovery should prove useful in deciphering the role of T2Rs within the cardiovascular system.
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Affiliation(s)
- Conor J Bloxham
- School of Biomedical Sciences, Faculty of Medicine, University of Queensland, QLD, Australia; Regenerative Medicine in Cardiovascular Diseases, First Department of Medicine, Klinikum rechts der Isar, Technical University of Munich, Germany
| | - Katina D Hulme
- School of Chemistry and Molecular Biosciences, Faculty of Science, University of Queensland, QLD, Australia; Department of Medical Microbiology, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Fabrizio Fierro
- Institute of Biochemistry, Food Science and Nutrition, The Hebrew University of Jerusalem, Israel
| | - Christian Fercher
- Australian Institute for Bioengineering and Nanotechnology, University of Queensland, QLD, Australia
| | - Cassandra L Pegg
- School of Chemistry and Molecular Biosciences, Faculty of Science, University of Queensland, QLD, Australia
| | - Shannon L O'Brien
- Institute of Metabolism and Systems Research, University of Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Simon R Foster
- School of Biomedical Sciences, Faculty of Medicine, University of Queensland, QLD, Australia; QIMR Berghofer Medical Research Institute, Herston, QLD, Australia
| | - Kirsty R Short
- School of Chemistry and Molecular Biosciences, Faculty of Science, University of Queensland, QLD, Australia
| | - Sebastian G B Furness
- School of Biomedical Sciences, Faculty of Medicine, University of Queensland, QLD, Australia; Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - Melissa E Reichelt
- School of Biomedical Sciences, Faculty of Medicine, University of Queensland, QLD, Australia
| | - Masha Y Niv
- Institute of Biochemistry, Food Science and Nutrition, The Hebrew University of Jerusalem, Israel
| | - Walter G Thomas
- School of Biomedical Sciences, Faculty of Medicine, University of Queensland, QLD, Australia.
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3
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Li Y, Langley N, Zhang J. Recent Advances in Bitterness-Sensing Systems. BIOSENSORS 2023; 13:bios13040414. [PMID: 37185489 PMCID: PMC10136117 DOI: 10.3390/bios13040414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 03/17/2023] [Accepted: 03/20/2023] [Indexed: 05/17/2023]
Abstract
Bitterness is one of the basic tastes, and sensing bitterness plays a significant role in mammals recognizing toxic substances. The bitter taste of food and oral medicines may decrease consumer compliance. As a result, many efforts have been made to mask or decrease the bitterness in food and oral pharmaceutical products. The detection of bitterness is critical to evaluate how successful the taste-masking technology is, and many novel taste-sensing systems have been developed on the basis of various interaction mechanisms. In this review, we summarize the progress of bitterness response mechanisms and the development of novel sensors in detecting bitterness ranging from commercial electronic devices based on modified electrodes to micro-type sensors functionalized with taste cells, polymeric membranes, and other materials in the last two decades. The challenges and potential solutions to improve the taste sensor quality are also discussed.
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Affiliation(s)
- Yanqi Li
- Cixi Institute of Biomedical Engineering, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
| | - Nigel Langley
- Gaylord Chemical Company LLC, 1404 Greengate Dr, Ste 100, Covington, LA 70433, USA
| | - Jiantao Zhang
- Cixi Institute of Biomedical Engineering, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
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4
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Topin J, Bouysset C, Pacalon J, Kim Y, Rhyu MR, Fiorucci S, Golebiowski J. Functional molecular switches of mammalian G protein-coupled bitter-taste receptors. Cell Mol Life Sci 2021; 78:7605-7615. [PMID: 34687318 PMCID: PMC11073308 DOI: 10.1007/s00018-021-03968-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 09/20/2021] [Accepted: 09/26/2021] [Indexed: 10/20/2022]
Abstract
Bitter taste receptors (TAS2Rs) are a poorly understood subgroup of G protein-coupled receptors (GPCRs). The experimental structure of these receptors has yet to be determined, and key-residues controlling their function remain mostly unknown. We designed an integrative approach to improve comparative modeling of TAS2Rs. Using current knowledge on class A GPCRs and existing experimental data in the literature as constraints, we pinpointed conserved motifs to entirely re-align the amino-acid sequences of TAS2Rs. We constructed accurate homology models of human TAS2Rs. As a test case, we examined the accuracy of the TAS2R16 model with site-directed mutagenesis and in vitro functional assays. This combination of in silico and in vitro results clarifies sequence-function relationships and proposes functional molecular switches that encode agonist sensing and downstream signaling mechanisms within mammalian TAS2Rs sequences.
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Affiliation(s)
- Jérémie Topin
- Institut de Chimie de Nice UMR7272, Université Côte d'Azur, CNRS, Nice, France.
| | - Cédric Bouysset
- Institut de Chimie de Nice UMR7272, Université Côte d'Azur, CNRS, Nice, France
| | - Jody Pacalon
- Institut de Chimie de Nice UMR7272, Université Côte d'Azur, CNRS, Nice, France
| | - Yiseul Kim
- Korea Food Research Institute, 245 Iseo-myeon, Wanju-gun, Jeollabuk-do, 55365, Republic of Korea
| | - Mee-Ra Rhyu
- Korea Food Research Institute, 245 Iseo-myeon, Wanju-gun, Jeollabuk-do, 55365, Republic of Korea
| | - Sébastien Fiorucci
- Institut de Chimie de Nice UMR7272, Université Côte d'Azur, CNRS, Nice, France.
| | - Jérôme Golebiowski
- Institut de Chimie de Nice UMR7272, Université Côte d'Azur, CNRS, Nice, France
- Department of Brain and Cognitive Sciences, DGIST, 333, Techno JungAng, Daero, HyeongPoong Myeon, Daegu, 711-873, Republic of Korea
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5
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Liang Q, Shu F, Dong X, Feng P. The evolution of a bitter taste receptor gene in primates. Chem Senses 2021; 46:6449468. [PMID: 34864939 DOI: 10.1093/chemse/bjab049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Bitter taste perception is critical to prevent animals from ingesting potentially harmful substances. The aim of this study was to characterize the evolution of T2R4 and test the hypothesis that different regions of the T2R gene are subject to disparate selective pressures, with extracellular regions (ECs) being erratic while transmembrane (TMs) and intracellular regions (ICs) being constrained. Thus, we examined the selective pressures acting on T2R4 and its different regions in 37 primates, and discovered that T2R4 and ECs were subject to neutral evolution and purifying selection, respectively, whereas both TMs and ICs showed purifying selection, as suggested by the hypothesis. We attribute this result to the relatively conservative property of T2R4 gene and the limited number of bitter tastants that T2R4 can respond to. Furthermore, we found that positive selection had acted on the first loop of extracellular regions (EL1). In contrast, the second loop (EL2) and transmembrane region-3, -6, -7 (TM367) were subject to purifying selection, and the third loop (EL3) was subject to neutral evolution. This discovery is probably because EL2, EL3, and TMs play a crucial role in the ligand-binding process, and EL1 is involved in the tastant recognition process. We further tested whether the ω of T2R4 differs among species with different diets and found that a specialized diet affected the evolution of T2R4. Feeding habits, fewer T2Rs, and a dietary shift may account for the results. This study can help to uncover the evolution of T2Rs during the primate evolutionary course.
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Affiliation(s)
- Qiufang Liang
- Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (Guangxi Normal University), Ministry of Education, Guilin, Guangxi, China.,Guangxi Key Laboratory of Rare and Endangered Animal Ecology, Guangxi Normal University, Guilin, Guangxi, China
| | - Fanglan Shu
- Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (Guangxi Normal University), Ministry of Education, Guilin, Guangxi, China.,Guangxi Key Laboratory of Rare and Endangered Animal Ecology, Guangxi Normal University, Guilin, Guangxi, China
| | - Xiaoyan Dong
- Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (Guangxi Normal University), Ministry of Education, Guilin, Guangxi, China.,Guangxi Key Laboratory of Rare and Endangered Animal Ecology, Guangxi Normal University, Guilin, Guangxi, China
| | - Ping Feng
- Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (Guangxi Normal University), Ministry of Education, Guilin, Guangxi, China.,Guangxi Key Laboratory of Rare and Endangered Animal Ecology, Guangxi Normal University, Guilin, Guangxi, China
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6
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Ahmad R, Dalziel JE. G Protein-Coupled Receptors in Taste Physiology and Pharmacology. Front Pharmacol 2020; 11:587664. [PMID: 33390961 PMCID: PMC7774309 DOI: 10.3389/fphar.2020.587664] [Citation(s) in RCA: 84] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 10/09/2020] [Indexed: 12/14/2022] Open
Abstract
Heterotrimeric G protein-coupled receptors (GPCRs) comprise the largest receptor family in mammals and are responsible for the regulation of most physiological functions. Besides mediating the sensory modalities of olfaction and vision, GPCRs also transduce signals for three basic taste qualities of sweet, umami (savory taste), and bitter, as well as the flavor sensation kokumi. Taste GPCRs reside in specialised taste receptor cells (TRCs) within taste buds. Type I taste GPCRs (TAS1R) form heterodimeric complexes that function as sweet (TAS1R2/TAS1R3) or umami (TAS1R1/TAS1R3) taste receptors, whereas Type II are monomeric bitter taste receptors or kokumi/calcium-sensing receptors. Sweet, umami and kokumi receptors share structural similarities in containing multiple agonist binding sites with pronounced selectivity while most bitter receptors contain a single binding site that is broadly tuned to a diverse array of bitter ligands in a non-selective manner. Tastant binding to the receptor activates downstream secondary messenger pathways leading to depolarization and increased intracellular calcium in TRCs, that in turn innervate the gustatory cortex in the brain. Despite recent advances in our understanding of the relationship between agonist binding and the conformational changes required for receptor activation, several major challenges and questions remain in taste GPCR biology that are discussed in the present review. In recent years, intensive integrative approaches combining heterologous expression, mutagenesis and homology modeling have together provided insight regarding agonist binding site locations and molecular mechanisms of orthosteric and allosteric modulation. In addition, studies based on transgenic mice, utilizing either global or conditional knock out strategies have provided insights to taste receptor signal transduction mechanisms and their roles in physiology. However, the need for more functional studies in a physiological context is apparent and would be enhanced by a crystallized structure of taste receptors for a more complete picture of their pharmacological mechanisms.
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Affiliation(s)
- Raise Ahmad
- Food Nutrition and Health Team, Food and Bio-based Products Group, AgResearch, Palmerston North, New Zealand
| | - Julie E Dalziel
- Food Nutrition and Health Team, Food and Bio-based Products Group, AgResearch, Palmerston North, New Zealand
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7
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Yuan G, Jing Y, Wang T, Fernandes VS, Xin W. The bitter taste receptor agonist-induced negative chronotropic effects on the Langendorff-perfused isolated rat hearts. Eur J Pharmacol 2020; 876:173063. [DOI: 10.1016/j.ejphar.2020.173063] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 02/29/2020] [Accepted: 03/10/2020] [Indexed: 11/27/2022]
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8
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Zhang Z, Gao X, Zhang Q, Li W. Constitutive activity of a spermine receptor is maintained by a single site in the C-terminal. Biochem Biophys Res Commun 2020; 526:389-395. [PMID: 32222281 DOI: 10.1016/j.bbrc.2020.03.053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 03/08/2020] [Indexed: 11/28/2022]
Abstract
Olfactory receptors are G-protein coupled receptors (GPCRs) that enable olfactory epithelia to detect odorants. These GPCRs may also show constitutive activity, which play important roles in the development and responses of odorant receptor neurons. However, little is known about the molecular characteristics that support the constitutive activities in olfactory receptors. Here, we characterize a pair of olfactory receptor orthologs that show similar ligand-dependent activity but different levels of constitutive activity, and elucidate the molecular characteristics that maintain the constitutive activity. Previously, PmTAAR348, a sea lamprey (Petromyzon marinus) olfactory receptor that is activated by the male sex pheromone spermine has been reported. In this study, we identified LmTAAR348 of Northeast Chinese lamprey (Lethenteron morii) as an ortholog of PmTAAR348. When expressed in HEK293T cell lines, both receptors showed similar levels of activation when exposed to spermine. However, the constitutive activity of LmTAAR348 was 100-fold higher than that of PmTAAR348. Using site-directed mutagenesis, we screened all 13 amino acid residues (aa) that differed between the two orthologs and found that a switch in position 340 reversed the constitutive activity levels between LmTAAR348 and PmTAAR348. Mutating the remaining 12 aa did not affect the ligand-dependent or constitutive activation. Moreover, both the ligand-dependent and constitutive activation of TAAR348 are Golf (G protein ⍺ subunit olfactory type) independent. We conclude that a single aa in the C-terminal maintains the constitutive activity in a spermine receptor.
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Affiliation(s)
- Zhe Zhang
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai, 201306, China; International Research Center for Marine Biosciences, Ministry of Science and Technology, Shanghai Ocean University, Shanghai, 201306, China; Shanghai Universities Key Laboratory of Marine Animal Taxonomy and Evolution, Shanghai Ocean University, Shanghai, 201306, China
| | - Xiang Gao
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai, 201306, China; International Research Center for Marine Biosciences, Ministry of Science and Technology, Shanghai Ocean University, Shanghai, 201306, China; Shanghai Universities Key Laboratory of Marine Animal Taxonomy and Evolution, Shanghai Ocean University, Shanghai, 201306, China
| | - Qinghua Zhang
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai, 201306, China; International Research Center for Marine Biosciences, Ministry of Science and Technology, Shanghai Ocean University, Shanghai, 201306, China; Shanghai Universities Key Laboratory of Marine Animal Taxonomy and Evolution, Shanghai Ocean University, Shanghai, 201306, China
| | - Weming Li
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI, 48824, USA.
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9
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Bloxham CJ, Foster SR, Thomas WG. A Bitter Taste in Your Heart. Front Physiol 2020; 11:431. [PMID: 32457649 PMCID: PMC7225360 DOI: 10.3389/fphys.2020.00431] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 04/08/2020] [Indexed: 12/11/2022] Open
Abstract
The human genome contains ∼29 bitter taste receptors (T2Rs), which are responsible for detecting thousands of bitter ligands, including toxic and aversive compounds. This sentinel function varies between individuals and is underpinned by naturally occurring T2R polymorphisms, which have also been associated with disease. Recent studies have reported the expression of T2Rs and their downstream signaling components within non-gustatory tissues, including the heart. Though the precise role of T2Rs in the heart remains unclear, evidence points toward a role in cardiac contractility and overall vascular tone. In this review, we summarize the extra-oral expression of T2Rs, focusing on evidence for expression in heart; we speculate on the range of potential ligands that may activate them; we define the possible signaling pathways they activate; and we argue that their discovery in heart predicts an, as yet, unappreciated cardiac physiology.
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Affiliation(s)
- Conor J Bloxham
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, St Lucia, QLD, Australia
| | - Simon R Foster
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Walter G Thomas
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, St Lucia, QLD, Australia
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10
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Shaik FA, Jaggupilli A, Chelikani P. Highly conserved intracellular H208 residue influences agonist selectivity in bitter taste receptor T2R14. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:183057. [PMID: 31493373 DOI: 10.1016/j.bbamem.2019.183057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 08/23/2019] [Accepted: 08/26/2019] [Indexed: 11/19/2022]
Abstract
Bitter taste receptors (T2Rs) are a specialized class of cell membrane receptors of the G protein-coupled receptor family and perform a crucial role in chemosensation. The 25 T2Rs in humans are activated by structurally diverse ligands of plant, animal and microbial origin. The mechanisms of activation of these receptors are poorly understood. Therefore, identification of structural determinants of T2Rs that regulate its efficacy could be beneficial in understanding the molecular mechanisms of T2R activation. In this work, we characterized a highly conserved histidine (H208), present at TM5-ICL3 region of T2R14 and its role in agonist-induced T2R14 signaling. Surprisingly, mutation of the conserved H208 (H208A) did not result in increased basal activity of T2R14, in contrast to similar H206A mutation in T2R4 that showed constitutive or basal activity. However, H208A mutation in T2R14 resulted in an increase in agonist-induced efficacy for Flufenamic acid (FFA). Interestingly, H208A did not affect the potency of another T2R14 agonist Diphenhydramine (DPH). The H208R compensatory mutation showed FFA response similar to wild-type T2R14. Molecular modeling suggests a FFA-induced shift in TM3 and TM5 helices of H208A, which changes the network of interactions connecting TM5-ICL3-TM6. This report identifies a crucial residue on the intracellular surface of T2Rs that is involved in bitter ligand selectivity. It also highlights the varied roles carried out by some conserved residues in different T2Rs.
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Affiliation(s)
- Feroz Ahmed Shaik
- Manitoba Chemosensory Biology Research Group, Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba, Winnipeg, MB, Canada
| | - Appalaraju Jaggupilli
- Manitoba Chemosensory Biology Research Group, Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba, Winnipeg, MB, Canada
| | - Prashen Chelikani
- Manitoba Chemosensory Biology Research Group, Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba, Winnipeg, MB, Canada.
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11
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Jaggupilli A, Singh N, De Jesus VC, Gounni MS, Dhanaraj P, Chelikani P. Chemosensory bitter taste receptors (T2Rs) are activated by multiple antibiotics. FASEB J 2018; 33:501-517. [PMID: 30011231 DOI: 10.1096/fj.201800521rr] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Many medications including antibiotics taste bitter. The potency of these antibiotics on the 25 bitter taste receptors (T2Rs) in humans remains poorly understood. Here we characterize by sensory and structure-function analyses how antibiotics frequently used to treat airway infections in cystic fibrosis activate multiple human T2Rs. The potency of the broad-spectrum antibiotics, tobramycin, levofloxacin, and azithromycin on the highly expressed T2Rs in airways, T2R4, T2R14, and T2R20 was pursued. The amino acids and structural features of T2R4, T2R14, and T2R20 important for antibiotic binding were characterized by mutational analysis in heterologous cell-based assays. Strikingly, extracellular loop 2 in T2Rs performs a key function in binding to antibiotics with contribution from residues in transmembrane helices. Our results suggest that different antibiotics activate multiple T2Rs with different potencies. An understanding of the nonantibiotic and physiologic effects mediated through T2Rs on the host cells is much needed.-Jaggupilli, A., Singh, N., De Jesus, V. C., Gounni, M. S., Dhanaraj, P., Chelikani, P. Chemosensory bitter taste receptors (T2Rs) are activated by multiple antibiotics.
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Affiliation(s)
- Appalaraju Jaggupilli
- Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba (CHRIM), Winnipeg, Manitoba, Canada
| | - Nisha Singh
- Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba (CHRIM), Winnipeg, Manitoba, Canada
| | - Vivianne Cruz De Jesus
- Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba (CHRIM), Winnipeg, Manitoba, Canada
| | - Mohamed Soussi Gounni
- Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba (CHRIM), Winnipeg, Manitoba, Canada
| | - Premnath Dhanaraj
- Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba (CHRIM), Winnipeg, Manitoba, Canada
| | - Prashen Chelikani
- Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba (CHRIM), Winnipeg, Manitoba, Canada
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12
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Jaggupilli A, Singh N, Jesus VCD, Duan K, Chelikani P. Characterization of the Binding Sites for Bacterial Acyl Homoserine Lactones (AHLs) on Human Bitter Taste Receptors (T2Rs). ACS Infect Dis 2018; 4:1146-1156. [PMID: 29799189 DOI: 10.1021/acsinfecdis.8b00094] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The 25 bitter taste receptors (T2Rs) in humans are novel players in mediating host-pathogen responses in the airways and innate immunity. The chemosensory T2Rs are expressed in different extraoral tissues and perform diverse pathophysiological roles from mediating bronchodilation to detecting bacterial infection in the airways. T2Rs were suggested to be activated by multiple bacterial quorum sensing molecules (QSMs). However, whether bacterial QSMs bind to T2Rs and the structural features on T2Rs has not yet been characterized. Here, we analyzed the taste sensory profiles of QSMs including acyl homoserine lactones (C4-AHL, C8-AHL, and 3-oxo-C12-AHL) and hydroxyquinolones (HHQ and NHQ) predominantly secreted by Gram-negative bacteria and characterized the candidate T2Rs interacting with different QSMs using structure-function approaches. The potency of the above QSMs for T2Rs significantly expressed in the airways, namely T2R4, T2R14, and T2R20, was characterized. 3-Oxo-C12-AHL activated T2R4, T2R14, and T2R20, while C8-AHL activated T2R4 and T2R14 with strong potency. The T2R amino acid residues involved in the interactions were characterized by molecular-model-guided site-directed mutagenesis. AHLs bind to a similar orthosteric site present on the extracellular surface in all three T2Rs with significant contributions from residues in extracellular loop 2. Our results reveal the mode of binding of AHLs for different T2Rs and provide biochemical insights into their interactions. This study will facilitate mechanistic studies aimed at understanding the role of these T2Rs as "sensors" of bacteria and in host-pathogen interactions.
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Affiliation(s)
- Appalaraju Jaggupilli
- Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children’s Hospital Research Institute of Manitoba (CHRIM), Winnipeg, MB R3E 0W4, Canada
| | - Nisha Singh
- Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children’s Hospital Research Institute of Manitoba (CHRIM), Winnipeg, MB R3E 0W4, Canada
| | - Vivianne Cruz De Jesus
- Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children’s Hospital Research Institute of Manitoba (CHRIM), Winnipeg, MB R3E 0W4, Canada
| | - Kangmin Duan
- Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children’s Hospital Research Institute of Manitoba (CHRIM), Winnipeg, MB R3E 0W4, Canada
| | - Prashen Chelikani
- Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children’s Hospital Research Institute of Manitoba (CHRIM), Winnipeg, MB R3E 0W4, Canada
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13
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Liu K, Jaggupilli A, Premnath D, Chelikani P. Plasticity of the ligand binding pocket in the bitter taste receptor T2R7. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:991-999. [PMID: 29355483 DOI: 10.1016/j.bbamem.2018.01.014] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 01/03/2018] [Accepted: 01/11/2018] [Indexed: 01/12/2023]
Abstract
Bitter taste receptors (T2Rs) are a group of 25 G protein-coupled receptors (GPCRs) in humans. The cognate agonists and the mechanism of ligand binding to the majority of the T2Rs remain unknown. Here we report the first structure-function analysis of T2R7 and study the ability of this receptor to bind to different agonists by site-directed mutagenesis. Screening of ligands for T2R7 in calcium based assays lead to the identification of novel compounds that activate this receptor. Quinine, diphenidol, dextromethorphan and diphenhydramine showed substantial activation of T2R7. Interestingly, these bitter compounds showed different pharmacological characteristics. To investigate the structural features in T2R7 that might contribute to the observed differences in agonist specificities, molecular model guided ligand docking and site-directed mutagenesis was pursued. Amino acids D65, D86, W89, N167, T169, W170, S181, T255 and E271 in the ligand-binding pocket were replaced and the mutants characterized pharmacologically. Our results suggest D86, S181 and W170 present on the extracellular side of transmembrane 3 (TM3), TM5 and in extracellular loop 2 (ECL2) are essential for agonist binding in T2R7. Mutations of these amino acids lead to loss-of-function. We also identified gain-of-function residues that are agonist specific. These results suggest that agonists bind at an extracellular site rather than deep within the TM core involving residues present in both ECL2 and TM helices in T2R7. Similar to majority of the Class A GPCRs, ECL2 in T2R7 plays a significant role in agonist binding and activation.
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Affiliation(s)
- Kun Liu
- From the Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba (CHRIM), Winnipeg, MB R3E 0W4. Canada
| | - Appalaraju Jaggupilli
- From the Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba (CHRIM), Winnipeg, MB R3E 0W4. Canada
| | - Dhanaraj Premnath
- From the Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba (CHRIM), Winnipeg, MB R3E 0W4. Canada
| | - Prashen Chelikani
- From the Manitoba Chemosensory Biology Research Group and Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba (CHRIM), Winnipeg, MB R3E 0W4. Canada.
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14
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Cholesterol modulates bitter taste receptor function. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2081-2087. [PMID: 27288892 DOI: 10.1016/j.bbamem.2016.06.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 06/02/2016] [Accepted: 06/07/2016] [Indexed: 11/20/2022]
Abstract
Bitter taste perception in humans is believed to act as a defense mechanism against ingestion of potential toxic substances. Bitter taste is perceived by 25 distinct bitter taste receptors (T2Rs) which belong to the family of G protein-coupled receptors (GPCRs). In the overall context of the role of membrane lipids in GPCR function, we show here that T2R4, a representative member of the bitter taste receptor family, displays cholesterol sensitivity in its signaling function. In order to gain further insight into cholesterol sensitivity of T2R4, we mutated two residues Tyr114(3.59) and Lys117(3.62) present in the cholesterol recognition amino acid consensus (CRAC) motif in T2R4 with alanines. We carried out functional characterization of the mutants by calcium mobilization, followed by cholesterol depletion and replenishment. CRAC motifs in GPCRs have previously been implicated in preferential cholesterol association. Our analysis shows that the CRAC motif represents an intrinsic feature of bitter taste receptors and is conserved in 22 out of 25 human T2Rs. We further demonstrate that Lys117, an important CRAC residue, is crucial in the reported cholesterol sensitivity of T2R4. Interestingly, cholesterol sensitivity of T2R4 was observed at quinine concentrations in the lower mM range. To the best of our knowledge, our results represent the first report addressing the molecular basis of cholesterol sensitivity in the function of taste receptors.
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15
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Upadhyaya JD, Chakraborty R, Shaik FA, Jaggupilli A, Bhullar RP, Chelikani P. The Pharmacochaperone Activity of Quinine on Bitter Taste Receptors. PLoS One 2016; 11:e0156347. [PMID: 27223611 PMCID: PMC4880206 DOI: 10.1371/journal.pone.0156347] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 05/12/2016] [Indexed: 11/19/2022] Open
Abstract
Bitter taste is one of the five basic taste sensations which is mediated by 25 bitter taste receptors (T2Rs) in humans. The mechanism of bitter taste signal transduction is not yet elucidated. The cellular processes underlying T2R desensitization including receptor internalization, trafficking and degradation are yet to be studied. Here, using a combination of molecular and pharmacological techniques we show that T2R4 is not internalized upon agonist treatment. Pretreatment with bitter agonist quinine led to a reduction in subsequent quinine-mediated calcium responses to 35 ± 5% compared to the control untreated cells. Interestingly, treatment with different bitter agonists did not cause internalization of T2R4. Instead, quinine treatment led to a 2-fold increase in T2R4 cell surface expression which was sensitive to Brefeldin A, suggesting a novel pharmacochaperone activity of quinine. This phenomenon of chaperone activity of quinine was also observed for T2R7, T2R10, T2R39 and T2R46. Our results suggest that the observed action of quinine for these T2Rs is independent of its agonist activity. This study provides novel insights into the pharmacochaperone activity of quinine and possible mechanism of T2R desensitization, which is of fundamental importance in understanding the mechanism of bitter taste signal transduction.
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Affiliation(s)
- Jasbir D. Upadhyaya
- Department of Oral Biology, and Manitoba Chemosensory Biology (MCSB) Research group, University of Manitoba, Winnipeg, MB, R3E 0W2, Canada
- Children’s Hospital Research Institute of Manitoba, Winnipeg, MB, R3E 3P4, Canada
| | - Raja Chakraborty
- Department of Oral Biology, and Manitoba Chemosensory Biology (MCSB) Research group, University of Manitoba, Winnipeg, MB, R3E 0W2, Canada
- Children’s Hospital Research Institute of Manitoba, Winnipeg, MB, R3E 3P4, Canada
| | - Feroz A. Shaik
- Department of Oral Biology, and Manitoba Chemosensory Biology (MCSB) Research group, University of Manitoba, Winnipeg, MB, R3E 0W2, Canada
- Children’s Hospital Research Institute of Manitoba, Winnipeg, MB, R3E 3P4, Canada
| | - Appalaraju Jaggupilli
- Department of Oral Biology, and Manitoba Chemosensory Biology (MCSB) Research group, University of Manitoba, Winnipeg, MB, R3E 0W2, Canada
- Children’s Hospital Research Institute of Manitoba, Winnipeg, MB, R3E 3P4, Canada
| | - Rajinder P. Bhullar
- Department of Oral Biology, and Manitoba Chemosensory Biology (MCSB) Research group, University of Manitoba, Winnipeg, MB, R3E 0W2, Canada
| | - Prashen Chelikani
- Department of Oral Biology, and Manitoba Chemosensory Biology (MCSB) Research group, University of Manitoba, Winnipeg, MB, R3E 0W2, Canada
- Children’s Hospital Research Institute of Manitoba, Winnipeg, MB, R3E 3P4, Canada
- * E-mail:
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16
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Singla R, Jaitak V. Synthesis of rebaudioside A from stevioside and their interaction model with hTAS2R4 bitter taste receptor. PHYTOCHEMISTRY 2016; 125:106-111. [PMID: 26976334 DOI: 10.1016/j.phytochem.2016.03.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 01/15/2016] [Accepted: 03/07/2016] [Indexed: 06/05/2023]
Abstract
Steviol glycosides (SG's) from Stevia rebaudiana (Bertoni) have been used as a natural low-calorie sweeteners. Its aftertaste bitterness restricts its use for human consumption and limits its application in food and pharmaceutical products. In present study, we have performed computational analysis in order to investigate the interaction of two major constituents of SG's against homology model of the hTAS2R4 receptor. Molecular simulation study was performed using stevioside and rebaudioside A revealed that, sugar moiety at the C-3'' position in rebaudioside A causes restriction of its entry into the receptor site thereby unable to trigger the bitter reception signaling cascade. Encouraged by the current finding, we have also developed a greener route using β-1,3-glucanase from Irpex lacteus for the synthesis of de-bittered rebaudioside A from stevioside. The rebaudioside A obtained was of high quality with percent conversion of 62.5%. The results here reported could be used for the synthesis of rebaudioside A which have large application in food and pharmaceutical industry.
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Affiliation(s)
- Ramit Singla
- Centre for Pharmaceutical Sciences and Natural Products, School of Basic and Applied Sciences, Central University of Punjab, Bathinda(Pb) 151 001, India
| | - Vikas Jaitak
- Centre for Pharmaceutical Sciences and Natural Products, School of Basic and Applied Sciences, Central University of Punjab, Bathinda(Pb) 151 001, India.
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17
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Bitter taste receptors: Novel insights into the biochemistry and pharmacology. Int J Biochem Cell Biol 2016; 77:184-96. [PMID: 26995065 DOI: 10.1016/j.biocel.2016.03.005] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 03/14/2016] [Accepted: 03/15/2016] [Indexed: 01/14/2023]
Abstract
Bitter taste receptors (T2Rs) belong to the super family of G protein-coupled receptors (GPCRs). There are 25 T2Rs expressed in humans, and these interact with a large and diverse group of bitter ligands. T2Rs are expressed in many extra-oral tissues and can perform diverse physiological roles. Structure-function studies led to the identification of similarities and dissimilarities between T2Rs and Class A GPCRs including amino acid conservation and novel motifs. However, the efficacy of most of the T2R ligands is not yet elucidated and the biochemical pharmacology of T2Rs is poorly understood. Recent studies on T2Rs characterized novel ligands including blockers for these receptors that include inverse agonist and antagonists. In this review we discuss the techniques used for elucidating bitter blockers, concept of ligand bias, generic amino acid numbering, the role of cholesterol, and conserved water molecules in the biochemistry and pharmacology of T2Rs.
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