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Abstract
The chapter presents an argument supporting the view that taste, defined as the receptor-mediated signaling of taste cells and consequent sensory events, is proper subject matter for the field of pharmacology. The argument develops through a consideration of how the field of pharmacology itself is to be defined. Though its application toward the discovery and development of therapeutics is of obvious value, pharmacology nevertheless is a basic science committed to examining biological phenomena controlled by the selective interactions between chemicals - regardless of their sources or uses - and receptors. The basic science of pharmacology is founded on the theory of receptor occupancy, detailed here in the context of taste. The discussion then will turn to consideration of the measurement of human taste and how well the results agree with the predictions of receptor theory.
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Palmer RK, Stewart MM, Talley J. Rapid Throughput Concentration-Response Analysis of Human Taste Discrimination. J Pharmacol Exp Ther 2021; 377:133-145. [PMID: 33468642 DOI: 10.1124/jpet.120.000373] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2020] [Accepted: 01/13/2021] [Indexed: 11/22/2022] Open
Abstract
Human taste threshold measurements often are used to infer tastant receptor functionality. However, taste thresholds can be influenced by receptor-independent variables. Examination of the full range of taste-active concentrations by taste discrimination has been hampered by logistics of testing multiple concentrations in replicate with human subjects. We developed an automated rapid throughput operant methodology for taste discrimination and applied it to concentration-response analysis of human taste. Tastant solutions (200 µl) drawn from a 96-well plate and self-administered to the tongue served as discriminative stimuli for money-reinforced responses on a touch-sensitive display. Robust concentration-response functions for "basic taste" stimuli were established, with particular focus on agonists of the taste 1 receptor member 2-taste 1 receptor member 3 heterodimer receptor (TAS1R2/R3). With a training cue of 100 mM sucrose, EC50 values of 56, 79, and 310 µM and 40 mM were obtained for rebaudioside A, sucralose, acesulfame potassium, and sucrose, respectively. Changing the sucrose training cue to 300 mM had no impact, but changing to 30 mM resulted in slight leftward shifts in potencies. A signal detection method also was used to determine values of d', a probabilistic value for discriminability, which indicated that 5 mM was near the limits of detection for sucrose. With repeated testing, both EC50 values and 5 mM sucrose d' values were established for each individual subject. The results showed little correspondence between threshold sensitivities and EC50 values for sucrose. We conclude that concentration-response analysis of taste discrimination provides a more reliable means of inferring receptor function than measurement of discriminability at the lowest detectable tastant concentrations. SIGNIFICANCE STATEMENT: Many inferences about human tastant receptor functionality have been made from taste threshold measurements, which can be influenced by variables unrelated to receptors. We herein report a new methodology that enables rigorous concentration-response analysis of human taste discrimination and its use toward quantitative characterization of tastant agonist activity. Our data suggest that taste discrimination concentration-response functions are a more reliable reflection of underlying receptor activity than threshold measures obtained at the lowest detectable tastant concentrations.
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Affiliation(s)
- R Kyle Palmer
- Opertech Bio, Inc., Pennovation Center, Philadelphia, Pennsylvania
| | - Mariah M Stewart
- Opertech Bio, Inc., Pennovation Center, Philadelphia, Pennsylvania
| | - John Talley
- Opertech Bio, Inc., Pennovation Center, Philadelphia, Pennsylvania
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Stewart MM, Palmer RK. Automated High Throughput Objective Assessment of Human Taste Palatability Predictive of Consumption. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.665.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
The study of taste has been guided throughout much of its history by the conceptual framework of psychophysics, where the focus was on quantification of the subjective experience of the taste sensations. By the mid-20th century, data from physiologic studies had accumulated sufficiently to assemble a model for the function of receptors that must mediate the initial stimulus of tastant molecules in contact with the tongue. But the study of taste as a receptor-mediated event did not gain momentum until decades later when the actual receptor proteins and attendant signaling mechanisms were identified and localized to the highly specialized taste-responsive cells of the tongue. With those discoveries a new opportunity to examine taste as a function of receptor activity has come into focus. Pharmacology is the science designed specifically for the experimental interrogation and quantitative characterization of receptor function at all levels of inquiry from molecules to behavior. This review covers the history of some of the major concepts that have shaped thinking and experimental approaches to taste, the seminal discoveries that have led to elucidation of receptors for taste, and how applying principles of receptor pharmacology can enhance understanding of the mechanisms of taste physiology and perception.
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Affiliation(s)
- R Kyle Palmer
- Opertech Bio, Inc., Pennovation Center, Philadelphia, Pennsylvania
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Palmer RK, Long D, Brennan F, Buber T, Bryant R, Salemme FR. A high throughput in vivo assay for taste quality and palatability. PLoS One 2013; 8:e72391. [PMID: 23951319 PMCID: PMC3741146 DOI: 10.1371/journal.pone.0072391] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 07/09/2013] [Indexed: 02/02/2023] Open
Abstract
Taste quality and palatability are two of the most important properties measured in the evaluation of taste stimuli. Human panels can report both aspects, but are of limited experimental flexibility and throughput capacity. Relatively efficient animal models for taste evaluation have been developed, but each of them is designed to measure either taste quality or palatability as independent experimental endpoints. We present here a new apparatus and method for high throughput quantification of both taste quality and palatability using rats in an operant taste discrimination paradigm. Cohorts of four rats were trained in a modified operant chamber to sample taste stimuli by licking solutions from a 96-well plate that moved in a randomized pattern beneath the chamber floor. As a rat's tongue entered the well it disrupted a laser beam projecting across the top of the 96-well plate, consequently producing two retractable levers that operated a pellet dispenser. The taste of sucrose was associated with food reinforcement by presses on a sucrose-designated lever, whereas the taste of water and other basic tastes were associated with the alternative lever. Each disruption of the laser was counted as a lick. Using this procedure, rats were trained to discriminate 100 mM sucrose from water, quinine, citric acid, and NaCl with 90-100% accuracy. Palatability was determined by the number of licks per trial and, due to intermediate rates of licking for water, was quantifiable along the entire spectrum of appetitiveness to aversiveness. All 96 samples were evaluated within 90 minute test sessions with no evidence of desensitization or fatigue. The technology is capable of generating multiple concentration-response functions within a single session, is suitable for in vivo primary screening of tastant libraries, and potentially can be used to evaluate stimuli for any taste system.
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Affiliation(s)
- R. Kyle Palmer
- Opertech Bio, Inc., Philadelphia, Pennsylvania, United States of America
- * E-mail:
| | - Daniel Long
- Opertech Bio, Inc., Philadelphia, Pennsylvania, United States of America
| | - Francis Brennan
- Genomind, LLC, Chalfont, Pennsylvania, United States of America
| | - Tulu Buber
- Opertech Bio, Inc., Philadelphia, Pennsylvania, United States of America
| | - Robert Bryant
- Asheville Flavor Innovations, LLC, Asheville, North Carolina, United State of America
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Kyle Palmer R, A. Lunn C. TRP Channels as Targets for Therapeutic Intervention in Obesity: Focus on TRPV1 and TRPM5. Curr Top Med Chem 2013; 13:247-57. [DOI: 10.2174/15680266113139990089] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 01/18/2013] [Indexed: 11/22/2022]
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C. Pawlyk A, Kyle Palmer R, Sprous D, Allee C. A Generalized Model and High Throughput Data Analysis System for Functional Modulation of Receptor-Agonist Systems Suitable for use in Drug Discovery. Comb Chem High Throughput Screen 2013; 16:199-209. [DOI: 10.2174/1386207311316030005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Revised: 06/26/2012] [Accepted: 07/24/2012] [Indexed: 11/22/2022]
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Palmer RK, Atwal K, Bakaj I, Carlucci-Derbyshire S, Buber MT, Cerne R, Cortés RY, Devantier HR, Jorgensen V, Pawlyk A, Lee SP, Sprous DG, Zhang Z, Bryant R. Triphenylphosphine oxide is a potent and selective inhibitor of the transient receptor potential melastatin-5 ion channel. Assay Drug Dev Technol 2011; 8:703-13. [PMID: 21158685 DOI: 10.1089/adt.2010.0334] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
Transient receptor potential melastatin-5 (TRPM5) is a calcium-gated monovalent cation channel expressed in highly specialized cells of the taste bud and gastrointestinal tract, as well as in pancreatic β-cells. Well established as a critical signaling protein for G protein-coupled receptor-mediated taste pathways, TRPM5 also has recently been implicated as a regulator of incretin and insulin secretion. To date, no inhibitors of practical use have been described that could facilitate investigation of TRPM5 functions in taste or secretion of metabolic hormones. Using recombinant TRPM5-expressing cells in a fluorescence imaging plate reader-based membrane potential assay, we identified triphenylphosphine oxide (TPPO) as a selective and potent inhibitor of TRPM5. TPPO inhibited both human (IC₅₀ = 12 μM) and murine TRPM5 (IC₅₀ = 30 μM) heterologously expressed in HEK293 cells, but had no effect (up to 100 μM) on the membrane potential responses of TRPA1, TRPV1, or TRPM4b. TPPO also inhibited a calcium-gated TRPM5-dependent conductance in taste cells isolated from the tongues of transgenic TRPM5(+/)⁻ mice. In contrast, TPP had no effect on TRPM5 responses, indicating a strict requirement of the oxygen atom for activity. Sixteen additional TPPO derivatives also inhibited TRPM5 but none more potently than TPPO. Structure-activity relationship of tested compounds was used for molecular modeling-based analysis to clarify the positive and negative structural contributions to the potency of TPPO and its derivatives. TPPO is the most potent TRPM5 inhibitor described to date and is the first demonstrated to exhibit selectivity over other channels.
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Sprous DG, Palmer RK, Swanson JT, Lawless M. QSAR in the pharmaceutical research setting: QSAR models for broad, large problems. Curr Top Med Chem 2010; 10:619-37. [PMID: 20337590 DOI: 10.2174/156802610791111506] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Accepted: 02/01/2010] [Indexed: 11/22/2022]
Abstract
The field of quantitative structure activity relationships (QSAR) has evolved into an integral tool for pharmaceutical discovery. It is presently an accessible technology, as can be shown by the number papers which are easily found through PubMed literature searches. At one level, QSAR is used routinely and invisibly as an aid for the bench chemist for logP, logS, pK(a)/pK(b), metabolic stability and other such properties. Chemoinformaticians and computational chemists develop models from scratch for less routine purposes associated with lead optimization around a single target or library design around a target family such as kinase, ion channel or GPCR inhibitors. Regardless of the differences in frequency of use and the end user, any successful QSAR is successful because it rests on appropriate mathematics linking valid data and relevant descriptors. Though success is defined by the end user, the QSAR originator is well advised to validate his model and understand how it performs in different situations. The present review will cover QSAR from the ground up as it is used in pharmaceutical research environments. It will focus towards larger dataset methodologies (a minimum 100 of compounds) and by consequence will focus on 2D descriptors. It will start with the critical base of data, descriptors, equations and validation methods. It will review the broadly used and invisible QSARs for logP, pKa/pKb and metabolic stability. The review will then present progress in QSARs of broad interest which are under active development: 1) hERG liability models, 2) modeling for 2a) drug-likeness and related properties, 2b) kinase ligand likeness and 2c) GPCR ligand likeness.
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Long DJ, Devantier HR, Brennan FX, Bryant RW, Salemme FR, Palmer RK. Pharmacologic antagonism of the oral aversive taste-directed response to capsaicin in a mouse brief access taste aversion assay. J Pharmacol Exp Ther 2009; 332:525-30. [PMID: 19903834 DOI: 10.1124/jpet.109.155416] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Chemosensory signaling by the tongue is a primary determinant of ingestive behavior and is mediated by specific interactions between tastant molecules and G protein-coupled and ion channel receptors. The functional relationship between tastant and receptor should be amenable to pharmacologic methods and manipulation. We have performed a pharmacologic characterization of the taste-directed licking of mice presented with solutions of capsaicin and other transient receptor potential vanilloid-1 (TRPV1) agonists using a brief access taste aversion assay. Dose-response functions for lick-rate suppression were established for capsaicin (EC(50) = 0.5 microM), piperine (EC(50) = 2 muM), and resiniferatoxin (EC(50) = 0.02 microM). Little or no effect on lick rate was observed in response to the full TRPV1 agonist olvanil. Capsaicin lick rates of wild-type and transient receptor potential melastatin-5 (TRPM5) knockout mice were equivalent, indicating that TRPM5, a critical component of aversive signaling for many bitter tastants, did not contribute to the capsaicin taste response. The selective TRPV1 antagonists N-(4-tertiarybutylphenyl)-4-(3-chloropyridin-2-yl)tetrahydropyrazine-1(2H)-carbox-amide (10 microM) and (E)-3-(4-t-butylphenyl)-N-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)acrylamide (AMG9810) (10 microM) effectively blocked capsaicin- and piperine-mediated lick suppression. However, (E)-3-(4-chlorophenyl)-N-(3-methoxyphenyl)-N-phenylprop-2-enamide (SB 366791) and capsazepine, also TRPV1 antagonists, were without effect at test concentrations of up to 30 and 100 microM, respectively. Our results demonstrate that TRPV1-mediated oral aversiveness presents a pharmacologic profile differing from what has been reported previously for TRPV1 pain signaling and, furthermore, that aversive tastes can be evaluated and controlled pharmacologically.
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Affiliation(s)
- Daniel J Long
- Discovery Research, RedPoint Bio Corporation, Ewing, New Jersey, USA
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Abstract
Over the last decade, many of the molecular components that mediate the transduction of taste signaling have been elucidated. The chemosensory receptors for taste have been identified as G protein-coupled receptors (GPCRs) and ion channels that are expressed on the surface of highly specialized taste sensory cells. Tastant molecules act as agonists, binding to and stabilizing active conformations of receptors, resulting in the initiation of signal transduction cascades. Taste signaling, therefore, should be amenable to the methods of pharmacology. This review focuses on the GPCR-mediated signaling of bitter, sweet, and umami tastes and emphasizes the opportunities for pharmacologic evaluation.
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Affiliation(s)
- R Kyle Palmer
- Redpoint Bio Corporation, 2005 Eastpark Blvd., Cranbury, NJ 08512, USA.
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Fossetta J, Jackson J, Deno G, Fan X, Du XK, Bober L, Soudé-Bermejo A, de Bouteiller O, Caux C, Lunn C, Lundell D, Palmer RK. Pharmacological analysis of calcium responses mediated by the human A3 adenosine receptor in monocyte-derived dendritic cells and recombinant cells. Mol Pharmacol 2003; 63:342-50. [PMID: 12527805 DOI: 10.1124/mol.63.2.342] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Extensive characterization of adenosine receptors expressed by human monocyte-derived dendritic cells (MDDCs) was performed with quantitative polymerase chain reaction, radioligand binding, and calcium signaling. Transcript for the A3 adenosine receptor was elevated more than 100-fold in immature MDDCs compared with monocyte precursors. A3 receptor transcript was substantially diminished, and A2A receptor transcript increased, by lipopolysaccharide maturation of MDDCs. Saturation binding of N(6)-(3-[(125)I]iodo-4-aminobenzyl)-adenosine-5'-N-methyluronamide ([(125)I]AB-MECA) to membranes from immature MDDCs yielded B(max) of 298 fmol/mg of protein and K(D) of 0.7 nM. Competition against [(125)I]AB-MECA binding confirmed the site to be the A3 receptor. Adenosine elicited pertussis toxin-sensitive calcium responses with EC(50) values ranging as low as 2 nM. The order of potency for related agonists was N(6)-(3-iodobenzyl)-adenosine-5'-N-methylcarboxamide (IB-MECA) >/= I-AB-MECA > 2Cl-IB-MECA >/= adenosine > 2-[p-(2-carboxyethyl)phenylethylamino]-5'-N-ethylcarboxyamidoadenosine (CGS21680). The order of efficacy was adenosine >/= CGS21680 > IB-MECA >/= I-AB-MECA > 2Cl-IB-MECA. Calcium responses to 2Cl-IB-MECA and CGS21680, and the lower range of adenosine concentrations, were completely blocked by 10 nM N-(2-methoxyphenyl)-N-[2-(3-pyridyl)quinazolin-4-yl]urea (VUF5574) but not by 7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine (SCH58261) or 8-cyclopentyl-1,3-dipropylxanthine. Pretreatment with 100 nM 2Cl-IB-MECA eliminated responses to CGS21680 but not to monocyte inhibitory protein-1alpha. For comparison, dose-response functions were obtained from double-recombinant human embryonic kidney 293 cells expressing the human A3 receptor and a chimeric Galphaq-i3 protein, which was required to establish A3-mediated calcium signaling. The pharmacological profile of calcium signaling elicited by adenosine-related agonists in the double-recombinant cells was essentially identical to that obtained from immature MDDCs. Our results provide an extensive analysis of A3-mediated calcium signaling and unequivocally identify immature MDDCs as native expressers of the human A3 receptor.
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Affiliation(s)
- James Fossetta
- Immunology Department, Schering-Plough Research Institute, Kenilworth, New Jersey 07033, USA
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Palmer RK, Boyer JL, Schachter JB, Nicholas RA, Harden TK. Agonist action of adenosine triphosphates at the human P2Y1 receptor. Mol Pharmacol 1998; 54:1118-23. [PMID: 9855642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
The agonist selectivity for adenosine di- and triphosphates was determined for the human P2Y1 receptor stably expressed in human 1321N1 astrocytoma cells and was studied under conditions in which nucleotide metabolism was both minimized and assessed. Cells were grown at low density on glass coverslips, encased in a flow-through chamber, and continuously superfused with medium, and Ca2+ responses to nucleotides were quantified. Superfusion with high performance liquid chromatographically purified ADP, ATP, 2-methylthio-ADP, and 2-methylthio-ATP resulted in rapid Ca2+ responses, with EC50 values of 10 +/- 5, 304 +/- 51, 2 +/- 1, and 116 +/- 50 nM, respectively. Similar peak responses were observed with maximal concentrations of these four agonists and with the hydrolysis-resistant adenine nucleoside triphosphate adenosine-5'-O-(3-thiotriphosphate). No conversion of [3H]ATP to [3H]ADP occurred under these conditions. Similar full agonist activities of ATP, 2-methylthio-ATP, and ADP were observed in human embryonic kidney 293 cells, which natively express the P2Y1 receptor. In contrast to these results, Leon et al. [FEBS Lett 403:26-30 (1997)] and Hechler et al. [Mol Pharmacol 53:727-733 (1998)] recently reported that, whereas ADP and 2-methylthio-ADP were agonists, ATP and 2-methylthio-ATP were weak antagonists in studies of the human P2Y1 receptor expressed in human Jurkat cells. To assess whether differences in the degree of receptor reserve might explain this discrepancy of results, P2Y1 receptor-expressing 1321N1 cells were incubated for 24 hr with adenosine-5'-O-(2-thiodiphosphate), with the goal of down-regulating the level of functional receptors. Pretreatment with adenosine-5'-O-(2-thiodiphosphate) resulted in a 10-fold rightward shift in the concentration-effect curve for ADP; in contrast, the agonist activity of ATP was completely abolished. Taken together, our results indicate that adenosine di- and triphosphates are agonists at the human P2Y1 receptor. However, the intrinsic efficacy of ATP is less than that of ADP, and the capacity of ATP to activate second messenger responses through this receptor apparently depends on the degree of P2Y1 receptor reserve.
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Affiliation(s)
- R K Palmer
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7365, USA
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Palmer RK, Boyer JL, Schachter JB, Nicholas RA, Harden TK. Agonist Action of Adenosine Triphosphates at the Human P2Y1 Receptor. Mol Pharmacol 1998. [DOI: 10.1124/mol.54.6.1118] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Abstract
A P2Y receptor with 65% identity to mammalian P2Y6 receptors, termed the p2y3 receptor, was recently cloned from a chick brain cDNA library and was proposed to represent a novel P2Y receptor subtype [Mol Pharmacol 50:258-265 (1996)]. We cloned the turkey homologue of the chick p2y3 receptor, which shares high sequence identity (97.6%) with the chick receptor, and we stably expressed this receptor and the rat P2Y6 receptor in 1321N1 human astrocytoma cells. The capacities of uridine and adenine nucleotides to promote inositol phosphate accumulation and intracellular Ca2+ mobilization were determined for both receptors. UDP and 5-bromo-UDP were the most potent agonists and UTP was a less potent full agonist at both receptors. In contrast, adenine nucleotides and nucleotide derivatives were relatively more potent at the turkey p2y3 receptor than at the rat P2Y6 receptor. To determine whether the avian p2y3 receptor defined a new subtype of mammalian P2Y receptor or was a species homologue of the mammalian P2Y6 receptor, we screened two different human genomic libraries and a Southern blot with a p2y3 receptor probe, under low-stringency conditions that allowed the clear identification of the human P2Y6 receptor gene. Our data indicated that the human genome does not contain a receptor that is more homologous to the avian p2y3 receptor than the P2Y6 receptor. Taken together, these data further define the pharmacological selectivities of these UDP-selective receptors and strongly suggest that the avian p2y3 receptor is a species homologue of the mammalian P2Y6 receptor.
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Affiliation(s)
- Q Li
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7365, USA
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Abstract
[Table: see text] The P2Y receptor on turkey erythrocyte membranes was the first P2 receptor to be shown to activate phospholipase C (PLC) in a strictly guanine nucleotide-dependent manner and remains the only G protein-coupled P2 receptor for which G protein-coupling kinetics have been defined. This membrane receptor has provided a model system for detailed pharmacological analyses of a series of chain-extended 2-thioether derivatives of adenine nucleotides that exhibit remarkable selectivity and potency for P2Y receptors. This model system also has led recently to identification of a novel series of P2 receptor antagonists. The turkey erythrocyte receptor is the species homologue of the chick P2Y1 receptor originally cloned by Webb and coworkers [Webb et al., 1993]. We also have cloned the human homologue of the P2Y1 receptor, which exhibits identical pharmacological and second messenger signaling properties to that of the avian P2Y1 receptor.
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Affiliation(s)
- José L Boyer
- Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina
| | - Joel B Schachter
- Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina
| | - Susan M Sromek
- Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina
| | - R Kyle Palmer
- Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina
| | - Kenneth A Jacobson
- Molecular Recognition Section, Laboratory at Bioorganic Chemistry, NIDDK, National Institutes of Health, Bethesda, Maryland
| | - Robert A Nicholas
- Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina
| | - T Kendall Harden
- Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina
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Palmer RK, Yule DI, McEwen EL, Williams JA, Fisher SK. Intra- and intercellular calcium signaling in human neuroepithelioma cells. J Lipid Mediat Cell Signal 1996; 14:169-74. [PMID: 8906559 DOI: 10.1016/0929-7855(96)00522-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The characteristics of intra- and intercellular Ca2+ signaling in human SK-N-MCIXC neuroepithelioma cells have been examined by means of Fura-2 digital imaging microfluorimetry. When cells were exposed to maximally effective concentrations of either endothelin-1, ATP, norepinephrine or oxotremorine-M, the Ca2+ signals that accompany an increase in phosphoinositide turnover could be differentiated on the basis of their magnitude, shape and duration. When individual cells were microinjected with inositol 1,4,5-trisphosphate, a rise in [Ca2+]i was observed not only in the target cell, but also in neighboring cells. This intercellular propagation of Ca2+ signals was found to be mediated via the release of nucleotide di- and triphosphates which subsequently activate purinergic receptors linked to Ca2+ homeostasis on neighboring cells. These results indicate: (1) that agonist-specific Ca2+ 'signatures' are generated in SK-N-MCIXC cells; and (2) that an intercellular propagation of Ca2+ signals is triggered by a rise in [Ca2+]i.
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Affiliation(s)
- R K Palmer
- Department of Pharmacology, University of Michigan, Ann Arbor 48109-0632, USA
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Palmer RK, Yule DI, Shewach DS, Williams JA, Fisher SK. Paracrine mediation of calcium signaling in human SK-N-MCIXC neuroepithelioma cells. Am J Physiol 1996; 271:C43-53. [PMID: 8760029 DOI: 10.1152/ajpcell.1996.271.1.c43] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Paracrine-mediated Ca2+ signaling in SK-N-MCIXC neuroepithelioma cells was evaluated by means of two experimental paradigms. In the first, single SK-N-MCIXC cells were microinjected with inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] and cytoplasmic Ca2+ was monitored by fura 2 digital-imaging microfluorometry. In response to Ins(1,4,5)P3 or CaCl2, but not inositol 1,3,4-trisphosphate, an increase in cytoplasmic Ca2+ concentration ([Ca2+]i) was observed in injected cells and also in neighboring cells. The direction of intercellular propagation of Ca2+ signals was influenced by the presence of a flow in the extracellular medium and occurred in the absence of any detectable gap-junctional communication. The P2 purinoceptor antagonist suramin, but not antagonists of other phosphoinositide-linked receptors, blocked cell-to-cell Ca2+ signaling initiated by microinjections of Ins(1,4,5)P3. In the second paradigm, conditioned medium (CM) obtained from monolayers of SK-N-MCIXC cells elicited increases in [Ca2+]i when reapplied to cells on coverslips. The Ca(2+)-mobilizing activity of CM was reversibly antagonized by suramin and abolished by pretreatment with apyrase. The presence of nucleotide di- and triphosphates in CM was confirmed by high-performance liquid chromatography. We conclude that SK-N-MCIXC cells release nucleotides that then activate specific receptors on neighboring cells. A rise in [Ca2+]i in these cells, and subsequent additional release of nucleotides, serves to further the propagation of intercellular Ca2+ signals.
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Affiliation(s)
- R K Palmer
- Neuroscience Laboratory, University of Michigan, Ann Arbor 48104-1687, USA
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Palmer RK, Yule DI, McEwen EL, Williams JA, Fisher SK. Agonist-specific calcium signaling and phosphoinositide hydrolysis in human SK-N-MCIXC neuroepithelioma cells. J Neurochem 1994; 63:2099-107. [PMID: 7964729 DOI: 10.1046/j.1471-4159.1994.63062099.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Fura-2 digital imaging microfluorimetry was used to evaluate the Ca2+ signals generated in single clonal human neuroepithelioma cells (SK-N-MCIXC) in response to agonists that stimulate phosphoinositide hydrolysis. Addition of optimal concentrations of either endothelin-1 (ET-1), ATP, oxotremorine-M (Oxo-M), or norepinephrine (NE) all resulted in an increase in the concentration of cytosolic calcium (Ca2+i) but of different magnitudes (ET-1 = ATP > Oxo-M > NE). The Ca2+ signals elicited by the individual agonists also differed from each other in terms of their latency of onset, rate of rise and decay, and prevalence of a sustained phase of Ca2+ influx. The Ca2+ signals that occurred in response to ATP had a shorter latency and more rapid rates of rise and decay than those observed for the other three agonists. Furthermore, a sustained plateau phase of the Ca2+ signal, which was characteristic of the response to Oxo-M, was observed in < 40% of cells stimulated with ET-1 and absent from Ca2+ signals elicited after NE addition. Removal of extracellular Ca2+ enhanced the rate of decay of Ca2+ signals generated by ATP, ET-1, or Oxo-M and, when evident, abolished the sustained phase of Ca2+ influx. In the absence of extracellular Ca2+, NE elicited asynchronous multiple Ca2+ transients. In either the absence or presence of extracellular Ca2+-, > 94% of cells responded to ET-1 or ATP, whereas corresponding values for Oxo-M and NE were approximately 74 and approximately 48%.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- R K Palmer
- Neuroscience Laboratory, Mental Health Research Institute, Ann Arbor, Michigan 48104-1687
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Palmer RK, Rapundalo ST, Batley BL, Barnes AE, Singh S, Ryan MJ, Taylor DG. Disparity between blood pressure and PRA inhibition after administration of a renin inhibitor to anesthetized dogs: methodological considerations. Clin Exp Hypertens 1993; 15:663-81. [PMID: 8374609 DOI: 10.3109/10641969309041636] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A dissociation between changes in blood pressure (BP) and plasma renin activity (PRA) has been noted after administration of renin inhibitors. In the present study, the renin inhibitor PD 132002 was given to salt-deplete, anesthetized dogs. PRA was measured at pH 6.0 by a conventional angiotensin I (ANG I) RIA method (PRA-C) and by an ANG I antibody-trapping RIA method (PRA-AT) performed at pH 7.4. PD 132002 at 0.01, 0.1, 1, and 10 mg/kg IV, reduced BP by 3 +/- 2, 9 +/- 2, 24 +/- 4, and 39 +/- 4 mm Hg, respectively, (baseline of 136 +/- 8 mm Hg, N = 5), when infused IV over 30 minutes with a 30 minute recovery between doses. The BP response at 10 mg/kg equaled that of saralasin (20 micrograms/kg/min IV). PRA-AT (baseline of 20 +/- 6 ng ANG l/ml/hr, N = 4) was inhibited by 0%, 28% +/- 12%, 75% +/- 10%, and 97% +/- 1% at 0.01, 0.1, 1, and 10 mg/kg, respectively. Plasma concentrations of immunoreactive ANG II were also reduced dose-dependently and paralleled changes in BP. In contrast, PRA-C (baseline of 13 +/- 4 ng ANG l/ml/hr, N = 4) was inhibited by 82% +/- 8% at 0.01 mg/kg and by > 98% at higher doses. After a single dose of PD 132002 at 10 mg/kg infused over 30 minutes, BP recovery paralleled changes in immunoreactive ANG II and PRA-AT, yet PRA-C inhibition showed no recovery over the same time course. Our data support the conclusion that BP relates better to PRA-AT than PRA-C. Thus the dissociation sometimes observed in studies with renin inhibitors between changes in BP and PRA may be attributed to the assay used to determine PRA.
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Affiliation(s)
- R K Palmer
- Department of Pharmacology, Parke-Davis Pharmaceutical Research Division, Warner-Lambert Company, Ann Arbor, MI 48105
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Abstract
Rhesus monkeys were conditioned to press on levers and receive intravenous infusions of cocaine or ketamine. Experimental conditions provided several different doses of drug during each of two daily 130 min sessions; as a result, a dose-response curve relating rate of responding to dose/injection for self-administered drug was obtained within each session. Relative rate-maintaining effects of nomifensine and cocaine in monkeys on baseline conditions of cocaine self-administration, and rate-maintaining effects of ketamine, phencyclidine and MK-801 in monkeys on baseline conditions of ketamine self-administration, compared favorably with relative rate-maintaining effects of these substances obtained in more traditional paradigms.
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Affiliation(s)
- G Winger
- Department of Pharmacology, University of Michigan, Ann Arbor 48109
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Guillette W, Judge RD, Koehn E, Miller JE, Palmer RK, Tremblay JL. Committee report on economic, administrative and legal factors influencing the insurability and employability of patients with ischemic heart disease. J Am Coll Cardiol 1989; 14:1010-5. [PMID: 2529301 DOI: 10.1016/0735-1097(89)90483-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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