1
|
Receptor density influences ligand-induced dopamine D 2L receptor homodimerization. Eur J Pharmacol 2021; 911:174557. [PMID: 34626593 DOI: 10.1016/j.ejphar.2021.174557] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 09/03/2021] [Accepted: 09/10/2021] [Indexed: 01/23/2023]
Abstract
Chronic treatments with dopamine D2 receptor ligands induce fluctuations in D2 receptor density. Since D2 receptors tend to assemble as homodimers, we hypothesized that receptor density might influence constitutive and ligand-induced homodimerization. Using a nanoluciferase-based complementation assay to monitor dopamine D2L receptor homodimerization in a cellular model enabling the tetracycline-controlled expression of dopamine D2L receptors, we observed that increasing receptor density promoted constitutive dopamine D2L receptor homodimerization. Receptor full agonists promoted homodimerization, while antagonists and partial agonists disrupted dopamine D2L receptor homodimers. High receptor densities enhanced this inhibitory effect only for receptor antagonists. Taken together, our findings indicate that both receptor density and receptor ligands influence dopamine D2L receptor homodimerization, albeit excluding any strict correlation with ligands' intrinsic activity and highlighting further complexity to dopaminergic pharmacology.
Collapse
|
2
|
Kühhorn J, Hübner H, Gmeiner P. Bivalent dopamine D2 receptor ligands: synthesis and binding properties. J Med Chem 2011; 54:4896-903. [PMID: 21599022 DOI: 10.1021/jm2004859] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dopamine D(2) receptor homodimers might be of particular importance in the pathophysiology of schizophrenia and, thus, serve as promising target proteins for the discovery of atypical antipsychotics. A highly attractive approach to investigate and control GPCR dimerization may be provided by the exploration and characterization of bivalent ligands, which can act as molecular probes simultaneously binding two adjacent binding sites of a dimer. The synthesis of bivalent dopamine D(2) receptor ligands of type 1 is presented, incorporating the privileged structure of 1,4-disubstituted aromatic piperidines/piperazines (1,4-DAPs) and triazolyl-linked spacer elements. Radioligand binding studies provided diagnostic insights when Hill slopes close to two for bivalent ligands with particular spacer lengths and a comparative analysis with respective monovalent control ligands and unsymmetrically substituted analogues indicated a bivalent binding mode with a simultaneous occupancy of two neighboring binding sites.
Collapse
Affiliation(s)
- Julia Kühhorn
- Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich-Alexander University, Erlangen, Germany
| | | | | |
Collapse
|
3
|
Vidi PA, Ejendal KF, Przybyla JA, Watts VJ. Fluorescent protein complementation assays: new tools to study G protein-coupled receptor oligomerization and GPCR-mediated signaling. Mol Cell Endocrinol 2011; 331:185-93. [PMID: 20654687 PMCID: PMC2990800 DOI: 10.1016/j.mce.2010.07.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Revised: 06/07/2010] [Accepted: 07/13/2010] [Indexed: 11/29/2022]
Abstract
G protein-coupled receptor (GPCR) signaling is mediated by protein-protein interactions at multiple levels. The characterization of the corresponding protein complexes is therefore paramount to the basic understanding of GPCR-mediated signal transduction. The number of documented interactions involving GPCRs is rapidly growing, and appreciating the functional significance of these complexes is clearly the next challenge. New experimental approaches including protein complementation assays (PCAs) have recently been used to examine the composition, plasma membrane targeting, and desensitization of protein complexes involved in GPCR signaling. These methods also hold promise for better understanding of drug-induced effects on GPCR interactions. This review focuses on the application of fluorescent PCAs for the study of GPCR signaling. Potential applications of PCAs in high-content screens are also presented. Non-fluorescent PCA techniques as well as combined assays for the detection of ternary and quaternary protein complexes are briefly discussed.
Collapse
Affiliation(s)
- Pierre-Alexandre Vidi
- Department of Basic Medical Sciences, School of Veterinary Medicine, Purdue University
| | - Karin F.K. Ejendal
- Department of Medicinal Chemistry and Molecular Pharmacology, School of Pharmacy and Pharmaceutical Sciences, Purdue University
| | - Julie A. Przybyla
- Department of Medicinal Chemistry and Molecular Pharmacology, School of Pharmacy and Pharmaceutical Sciences, Purdue University
| | - Val J. Watts
- Department of Medicinal Chemistry and Molecular Pharmacology, School of Pharmacy and Pharmaceutical Sciences, Purdue University
- Correspondence should be addressed to Dr. Val J. Watts, Department of Medicinal Chemistry and Molecular Pharmacology, School of Pharmacy and Pharmaceutical Sciences, Purdue University, 575 Stadium Mall Drive, West Lafayette, IN 47907-2051. Phone: (765) 496-3872, Fax: (765) 494-1414
| |
Collapse
|
4
|
Sf9 cells: a versatile model system to investigate the pharmacological properties of G protein-coupled receptors. Pharmacol Ther 2010; 128:387-418. [PMID: 20705094 DOI: 10.1016/j.pharmthera.2010.07.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Accepted: 07/12/2010] [Indexed: 11/23/2022]
Abstract
The Sf9 cell/baculovirus expression system is widely used for high-level protein expression, often with the purpose of purification. However, proteins may also be functionally expressed in the defined Sf9 cell environment. According to the literature, the pharmacology of G-protein-coupled receptors (GPCRs) functionally reconstituted in Sf9 cells is similar to the receptor properties in mammalian cells. Sf9 cells express both recombinant GPCRs and G-proteins at much higher levels than mammalian cells. Sf9 cells can be grown in suspension culture, providing an inexpensive way of obtaining large protein amounts. Co-infection with various baculoviruses allows free combination of GPCRs with different G-proteins. The absence of constitutively active receptors in Sf9 cells provides an excellent signal-to background ratio in functional assays, allowing the detection of agonist-independent receptor activity and of small ligand-induced signals including partial agonistic and inverse agonistic effects. Insect cell Gα(i)-like proteins mostly do not couple productively to mammalian GPCRs. Thus, unlike in mammalian cells, Sf9 cells do not require pertussis toxin treatment to obtain a Gα(i)-free environment. Co-expression of GPCRs with Gα(i1), Gα(i2), Gα(i3) or Gα(o) in Sf9 cells allows the generation of a selectivity profile for these Gα(i/o)-isoforms. Additionally, GPCR-G-protein combinations can be compared with defined 1:1 stoichiometry by expressing GPCR-Gα fusion proteins. Sf9 cells can also be employed for ligand screening in medicinal chemistry programs, using radioligand binding assays or functional assays, like the steady-state GTPase- or [(35)S]GTPγS binding assay. This review shows that Sf9 cells are a versatile model system to investigate the pharmacological properties of GPCRs.
Collapse
|
5
|
Pisterzi LF, Jansma DB, Georgiou J, Woodside MJ, Chou JTC, Angers S, Raicu V, Wells JW. Oligomeric size of the m2 muscarinic receptor in live cells as determined by quantitative fluorescence resonance energy transfer. J Biol Chem 2010; 285:16723-38. [PMID: 20304928 PMCID: PMC2878013 DOI: 10.1074/jbc.m109.069443] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Revised: 03/07/2010] [Indexed: 11/06/2022] Open
Abstract
Fluorescence resonance energy transfer (FRET), measured by fluorescence intensity-based microscopy and fluorescence lifetime imaging, has been used to estimate the size of oligomers formed by the M(2) muscarinic cholinergic receptor. The approach is based on the relationship between the apparent FRET efficiency within an oligomer of specified size (n) and the pairwise FRET efficiency between a single donor and a single acceptor (E). The M(2) receptor was fused at the N terminus to enhanced green or yellow fluorescent protein and expressed in Chinese hamster ovary cells. Emission spectra were analyzed by spectral deconvolution, and apparent efficiencies were estimated by donor-dequenching and acceptor-sensitized emission at different ratios of enhanced yellow fluorescent protein-M(2) receptor to enhanced green fluorescent protein-M(2) receptor. The data were interpreted in terms of a model that considers all combinations of donor and acceptor within a specified oligomer to obtain fitted values of E as follows: n = 2, 0.495 +/- 0.019; n = 4, 0.202 +/- 0.010; n = 6, 0.128 +/- 0.006; n = 8, 0.093 +/- 0.005. The pairwise FRET efficiency determined independently by fluorescence lifetime imaging was 0.20-0.24, identifying the M(2) receptor as a tetramer. The strategy described here yields an explicit estimate of oligomeric size on the basis of fluorescence properties alone. Its broader application could resolve the general question of whether G protein-coupled receptors exist as dimers or larger oligomers. The size of an oligomer has functional implications, and such information can be expected to contribute to an understanding of the signaling process.
Collapse
Affiliation(s)
- Luca F. Pisterzi
- From The Leslie L. Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
| | - David B. Jansma
- the Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario M5S 3E1, Canada
| | - John Georgiou
- The Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada
| | - Michael J. Woodside
- the Imaging Facility, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada, and
| | - Judy Tai-Chieh Chou
- From The Leslie L. Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
| | - Stéphane Angers
- From The Leslie L. Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
| | - Valerică Raicu
- the Departments of Physics and Biological Sciences, University of Wisconsin, Milwaukee, Wisconsin 53211
| | - James W. Wells
- From The Leslie L. Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
| |
Collapse
|
6
|
Kara E, Lin H, Strange PG. Co-operativity in agonist binding at the D2 dopamine receptor: evidence from agonist dissociation kinetics. J Neurochem 2009; 112:1442-53. [PMID: 20050980 DOI: 10.1111/j.1471-4159.2009.06554.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
There is much evidence to suggest that G protein coupled receptors exist as oligomers but the relevance to their function is unclear. We have, therefore, examined the binding of the radiolabelled agonist [(3)H]NPA to membranes of CHO cells expressing the D(2) dopamine receptor in dissociation rate experiments. When [(3)H]NPA dissociation was started by dilution, the dissociation rate in the absence of sodium ions was unaffected by addition of the antagonist/inverse agonist (+)-butaclamol, but was accelerated by addition of agonists e.g. dopamine, suggesting that the receptor was not behaving as a monomer with a single binding site. The very low efficacy partial agonist, aripiprazole provided an intermediate level of acceleration of dissociation. [(3)H]NPA dissociation experiments started by addition of ligands without dilution gave a similar pattern. [(3)H]NPA dissociation could also be accelerated by GTP. Dissociation of [(3)H]NPA in the presence of GTP and dopamine provided a greater acceleration than for either modulator alone, suggesting synergistic effects related to receptor/G protein interaction. When [(3)H]NPA dissociation experiments were performed in the presence of sodium ions, dissociation was faster than in their absence but the rate still depended on the ligand present in the assay. Overall the data cannot be explained by a ternary complex model and are consistent with an oligomeric receptor in which binding of [(3)H]NPA, as an example of an agonist ligand, can be modulated co-operatively by ligands binding elsewhere in the oligomer. Interactions with G proteins also occurs providing further modulation of [(3)H]NPA binding. Both agonists and G proteins are proposed to modulate the oligomer by switching high affinity agonist binding sites to low affinity sites.
Collapse
Affiliation(s)
- Elodie Kara
- School of Pharmacy, University of Reading, Whiteknights, Reading, UK
| | | | | |
Collapse
|
7
|
Kim OJ. A single mutation at lysine 241 alters expression and trafficking of the D2 dopamine receptor. J Recept Signal Transduct Res 2009; 28:453-64. [PMID: 18946766 DOI: 10.1080/10799890802379410] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Ubiquitination of G protein-coupled receptors has been identified to regulate receptor signal transduction including agonist-induced internalization and sorting of internalized receptor for degradation or for recycling. Using co-immunoprecipitation and immunoblot analysis, I found that the membrane-associated D(2) dopamine receptor (DAR) is mono-ubiquitinated in the absence of an agonist following heterologous expression in human embryonic kidney cells (HEK293). By using site-directed mutagenesis, this report shows that the loss of lysine-241, K241A D(2) DAR reduced the amount of membrane-associated D(2) DAR. It is of interest that the K241A D(2) DAR also had a distinctly different ubiquitination pattern than the wild-type D(2) DAR. It is important to note that the ubiquitinated mutant D(2) DAR was degraded through ubiquitin-proteasome pathway. These data provide the factual evidence that a loss of lysine-241 of the D(2) DAR affects receptor ubiquitination and renders the protein susceptible to the proteasomal degradation.
Collapse
Affiliation(s)
- Ok-Jin Kim
- Department of Pharmacology and Toxicology, School of Pharmacy, University of Kansas, Lawrence, Kansas 66045-7582, USA.
| |
Collapse
|
8
|
Vidi PA, Chemel BR, Hu CD, Watts VJ. Ligand-dependent oligomerization of dopamine D(2) and adenosine A(2A) receptors in living neuronal cells. Mol Pharmacol 2008; 74:544-51. [PMID: 18524886 DOI: 10.1124/mol.108.047472] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Adenosine A(2A) and dopamine D(2) receptors (A(2A) and D(2)) associate in homo- and heteromeric complexes in the striatum, providing a structural basis for their mutual antagonism. At the cellular level, the portion of receptors engaging in homo- and heteromers, as well as the effect of persistent receptor activation or antagonism on the cell oligomer repertoire, are largely unknown. We have used bimolecular fluorescence complementation (BiFC) to visualize A(2A) and D(2) oligomerization in the Cath.a differentiated neuronal cell model. Receptor fusions to BiFC fluorescent protein fragments retained their function when expressed alone or in A(2A)/A(2A), D(2)/D(2), and A(2A)/D(2) BiFC pairs. Robust fluorescence complementation reflecting A(2A)/D(2) heteromers was detected at the cell membrane as well as in endosomes. In contrast, weaker BiFC signals, largely confined to intracellular domains, were detected with A(2A)/dopamine D(1) BiFC pairs. Multicolor BiFC was used to simultaneously visualize A(2A) and D(2) homo- and heteromers in living cells and to examine drug-induced changes in receptor oligomers. Prolonged D(2) stimulation with quinpirole lead to the internalization of D(2)/D(2) and A(2A)/D(2) oligomers and resulted in decreased A(2A)/D(2) relative to A(2A)/A(2A) oligomer formation. Opposing effects were observed in cells treated with D(2) antagonists or with the A(2A) agonist 5'-N-methylcarboxamidoadenosine (MECA). Subsequent radioreceptor binding analysis indicated that the drug-induced changes in oligomer formation were not readily explained by alterations in receptor density. These observations support the hypothesis that long-term drug exposure differentially alters A(2A)/D(2) receptor oligomerization and provide the first demonstration for the use of BiFC to monitor drug-modulated GPCR oligomerization.
Collapse
Affiliation(s)
- Pierre-Alexandre Vidi
- Dept. of Medicinal Chemistry and Molecular Pharmacology, Purdue University, 575 Stadium Mall Drive, West Lafayette, IN 47907, USA
| | | | | | | |
Collapse
|
9
|
Tomé M, Moreira E, Pérez-Fígares JM, Jiménez AJ. Presence of D1- and D2-like dopamine receptors in the rat, mouse and bovine multiciliated ependyma. J Neural Transm (Vienna) 2007; 114:983-94. [PMID: 17458496 DOI: 10.1007/s00702-007-0666-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2006] [Accepted: 02/15/2007] [Indexed: 12/25/2022]
Abstract
The multiciliated ependyma forms an epithelial-like layer that could act as a selective barrier between the brain parenchyma and cerebrospinal fluid. In the present study, tyrosine hydroxylase-containing fibres have been detected in the basal pole of the ependymal cells of the lateral ventricles of rat, mouse and calf. The use of antibodies against at least two different peptide sequences of each D(2), D(3), D(4) and D(5) dopamine receptor subtype has allowed their detection in: (i) sections of mouse, rat and bovine lateral ventricles, by means of immunocytochemistry; and (ii) membrane protein extracts obtained from the ependymal layer of the bovine lateral ventricles, using immunoblotting. The immunocytochemical study has shown the presence of all these subtypes of dopamine receptors in the ependymal cells. Immunoblotting demonstrated similar immunoreactive bands for all receptor subtypes in both ependymal and corpus striatum membrane extracts.
Collapse
Affiliation(s)
- M Tomé
- Departamento de Biología Celular, Genética y Fisiología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
| | | | | | | |
Collapse
|
10
|
Heinrich JN, Brennan J, Lai MH, Sullivan K, Hornby G, Popiolek M, Jiang LX, Pausch MH, Stack G, Marquis KL, Andree TH. Aplindore (DAB-452), a high affinity selective dopamine D2 receptor partial agonist. Eur J Pharmacol 2006; 552:36-45. [PMID: 17056032 DOI: 10.1016/j.ejphar.2006.08.063] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2006] [Revised: 08/25/2006] [Accepted: 08/29/2006] [Indexed: 11/17/2022]
Abstract
The pharmacology of aplindore (DAB-452) was characterized in CHO-K1 cells stably transfected with the human dopamine D(2) receptor short isoform (CHO-D(2s)) and in a behavioral model for post-synaptic agonism in rats. In [(3)H]-spiperone competition binding studies, aplindore showed high affinity for dopamine D(2) and D(3) receptors and low affinity for the dopamine D(4), serotonin (5-HT)(1A), 5-HT(2) receptors and the alpha1-adrenoceptor. The high potency partial agonist activity of aplindore was demonstrated in [(35)S]guanosine 5'-O-(3-thiotriphosphate) ([(35)S]GTPgammaS) binding, extracellular signal-regulated kinase (ERK)-phosphorylation and intracellular calcium flux assay using fluorometric plate reader ([Ca(2+)](i)-FLIPR) format. The [Ca(2+)](i)-FLIPR assay was conducted with CHO-D(2S) receptor cells also stably expressing chimeric G(alphaq/o)-proteins. In all assay modalities, the potencies and intrinsic activities of aplindore were lower than dopamine and higher than aripiprazole. In contrast to the [(35)S]GTPgammaS binding and ERK-phosphorylation assays, the [Ca(2+)](i)-FLIPR assay was able to detect the low partial agonist activity of SDZ 208-912. In unilaterally 6-hydroxydopamine (6-OHDA) lesioned rats, aplindore induced contralateral turning, which was blocked by the dopamine D(2) receptor antagonist raclopride. The dopamine D(2) receptor selective partial agonist profile of aplindore suggests that it should be effective for the treatment of dopaminergic-based disorders, such as schizophrenia and Parkinson's disease.
Collapse
MESH Headings
- Animals
- Binding, Competitive
- CHO Cells
- Calcium/metabolism
- Cricetinae
- Cricetulus
- Dopamine Agonists/metabolism
- Dopamine Agonists/pharmacology
- Dose-Response Relationship, Drug
- Extracellular Signal-Regulated MAP Kinases/metabolism
- GTP-Binding Protein alpha Subunits/genetics
- GTP-Binding Protein alpha Subunits/metabolism
- Guanosine 5'-O-(3-Thiotriphosphate)/metabolism
- Indoles/metabolism
- Indoles/pharmacology
- Male
- Motor Activity/drug effects
- Oxidopamine/toxicity
- Phosphorylation/drug effects
- Quinpirole/pharmacology
- Radioligand Assay
- Rats
- Rats, Sprague-Dawley
- Receptor, Serotonin, 5-HT1A/metabolism
- Receptors, Adrenergic, alpha-1/metabolism
- Receptors, Dopamine D2/agonists
- Receptors, Dopamine D2/genetics
- Receptors, Dopamine D2/metabolism
- Receptors, Dopamine D4/metabolism
- Receptors, Serotonin, 5-HT2/metabolism
- Substantia Nigra/drug effects
- Substantia Nigra/pathology
- Substantia Nigra/physiopathology
Collapse
Affiliation(s)
- Julia N Heinrich
- Discovery Neuroscience, Wyeth Research, CN8000, Princeton, NJ 08543-8000, USA.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Uustare A, Reinart R, Rinken A. Modulation of dopamine D1 receptor signaling by adenosine A1 receptors in Sf9 cells requires expression of Gi proteins. Neurosci Lett 2006; 406:169-73. [PMID: 16935419 DOI: 10.1016/j.neulet.2006.07.051] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2006] [Revised: 06/27/2006] [Accepted: 07/07/2006] [Indexed: 11/19/2022]
Abstract
There are several evidences that some functions of D1 dopamine receptors can be modulated by colocalized adenosine A1 receptors. To elucidate the role of particular components of the receptor complex in the ligand binding and second messenger activation level we have used Sf9 cell expression system. The expression of D1 and A1 receptors was confirmed by proper binding of specific radioligands [3H]SCH23390 (Kd=1.1+/-0.1 nM, Bmax=2.2+/-0.1 pmol/mg protein) and [3H]DPCPX (Kd=2.1+/-0.8nM, Bmax=2.9+/-0.4 pmol/mg protein), respectively. The kinetics of [3H]SCH23390 binding corresponded to the simplest reversible bimolecular binding reaction of complex formation, with k(on)=0.20+/-0.02 min(-1)nM(-1) and k(off)=0.13+/-0.01 min(-1). Dopaminergic agonists increased the accumulation of cAMP in the transfected cells in concentration-dependent manner, indicating a correct coupling of receptor to second messenger system. The coupling of the A1 receptor to Gi proteins was confirmed by both GTPgammaS dependent agonist binding and inhibition of cAMP accumulation by N-cyclopentyladenosine (NCPA). Activation of the A1 receptor by NCPA had no significant influence on neither affinities of dopaminergic ligands nor the radioligand binding kinetics to the co-exprssed D1 receptors in Sf9 cell membranes. On the other hand, the activation of the A1 receptors inhibited the D1 receptor-specific accumulation of cAMP, but only in cells where Gi proteins were expressed with the receptors.
Collapse
MESH Headings
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/pharmacology
- Adenosine/analogs & derivatives
- Adenosine/pharmacology
- Adenosine A1 Receptor Antagonists
- Animals
- Benzazepines/pharmacokinetics
- Binding, Competitive/drug effects
- Cell Line
- Cyclic AMP/metabolism
- Dopamine Agonists/pharmacology
- Dopamine Antagonists/pharmacokinetics
- Dose-Response Relationship, Drug
- Drug Interactions
- GTP-Binding Protein alpha Subunits, Gi-Go/genetics
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Gene Expression/drug effects
- Gene Expression/physiology
- Guanosine 5'-O-(3-Thiotriphosphate)/pharmacology
- Humans
- Radioligand Assay/methods
- Receptor, Adenosine A1/physiology
- Receptors, Dopamine D1/physiology
- Signal Transduction/physiology
- Spodoptera
- Transfection/methods
- Tritium/pharmacokinetics
- Xanthines/pharmacokinetics
Collapse
Affiliation(s)
- Ain Uustare
- Institute of Organic and Bioorganic Chemistry, University of Tartu, Tartu, Estonia
| | | | | |
Collapse
|
12
|
Vivo M, Lin H, Strange PG. Investigation of Cooperativity in the Binding of Ligands to the D2Dopamine Receptor. Mol Pharmacol 2005; 69:226-35. [PMID: 16204468 DOI: 10.1124/mol.105.012443] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The D(2) dopamine receptor exists as dimers or as higher-order oligomers, as determined from data from physical experiments. In this study, we sought evidence that this oligomerization leads to cooperativity by examining the binding of three radioligands ([(3)H]nemonapride, [(3)H]raclopride, and [(3)H]spiperone) to D(2) dopamine receptors expressed in membranes of Sf9 cells. In saturation binding experiments, the three radioligands exhibited different B(max) values, and the B(max) values could be altered by the addition of sodium ions to assays. Despite labeling different numbers of sites, the different ligands were able to achieve full inhibition in competition experiments. Some ligand pairs also exhibited complex inhibition curves in these experiments. In radioligand dissociation experiments, the rate of dissociation of [(3)H]nemonapride or [(3)H]spiperone depended on the sodium ion concentration but was independent of the competing ligand. Although some of the data in this study are consistent with the behavior of a cooperative oligomeric receptor, not all of the data are in agreement with this model. It may, therefore, be necessary to consider more complex models for the behavior of this receptor.
Collapse
Affiliation(s)
- Meritxell Vivo
- School of Animal and Microbial Sciences, University of Reading, Whiteknights, Reading, RG6 6AJ, UK
| | | | | |
Collapse
|
13
|
Hemmilä I, Laitala V. Progress in Lanthanides as Luminescent Probes. J Fluoresc 2005; 15:529-42. [PMID: 16167211 DOI: 10.1007/s10895-005-2826-6] [Citation(s) in RCA: 333] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2004] [Accepted: 03/01/2005] [Indexed: 12/20/2022]
Abstract
Lanthanides have recently found applications in different fields of biomolecular and medical research. Luminescent lanthanide chelates have created interest mainly due to their unique luminescent properties, such as their long Stokes' shift and exceptional decay times allowing efficient temporal discrimination of background interferences in the assays, such as immunoassays. Recently, new organometallic complexes have been developed giving opportunities to novel applications, in heterogeneous and homogeneous immunoassays, DNA hybridization assays, high-throughput screening as well as in imaging. In addition, encapsulating the chelates into suitable matrix in beads enables the use of new members of lanthanides extending the emission wavelength to micrometer range and decays from a few microseconds to milliseconds. As the luminescence is derived from complicated intra-chelate energy transfer, it also gives novel opportunities to exploit these levels in different types of energy transfer based applications. This review gives a short overview of recent development of lanthanide chelate-labels and discusses in more details of energy levels and their exploitation in new assay formats.
Collapse
Affiliation(s)
- I Hemmilä
- Perkin Elmer Life and Analytical Sciences, Wallac Oy, P.O. Box 10, FIN-20101, Turku, Finland.
| | | |
Collapse
|
14
|
Handl HL, Gillies RJ. Lanthanide-based luminescent assays for ligand-receptor interactions. Life Sci 2005; 77:361-71. [PMID: 15894006 DOI: 10.1016/j.lfs.2005.01.009] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2004] [Accepted: 01/05/2005] [Indexed: 11/17/2022]
Abstract
The evaluation of receptor ligand interactions is important in the field of drug discovery and development. Currently these interactions are typically measured with cumbersome (low throughput) radiolabels. Higher throughput screens are available such as fluorescent measurements of G-protein coupled receptor-induced Ca2+ increases or fluorescence anisotropy, yet these have limited applicability and/or low signal to noise. Hence, there is a need to develop more widely applicable and more sensitive labels that can be used to monitor ligand-receptor interactions. Lanthanides provide an attractive alternative to the traditional labels used for monitoring ligand-receptor interactions. The incorporation of lanthanide labels into traditional assays used to assess receptor-ligand interactions can make these assays more affordable, less time consuming and amenable to automation. Lanthanides can be coupled to ligands and provide strong luminescent signals that can be detected using time-resolved fluorescence (TRF) methods. This approach takes advantage of the long fluorescence lifetime of the lanthanide and can detect less than one attomole of europium in a multiwell plate sample. This short review provides a basic introduction into lanthanides and TRF and describes some of the recent assays which have utilized lanthanides as labels to assess ligand-receptor interactions.
Collapse
Affiliation(s)
- Heather L Handl
- Arizona Cancer Center, P.O. Box 245024, 1515 N. Campbell, Tucson, AZ 85724, USA
| | | |
Collapse
|
15
|
Percherancier Y, Berchiche YA, Slight I, Volkmer-Engert R, Tamamura H, Fujii N, Bouvier M, Heveker N. Bioluminescence resonance energy transfer reveals ligand-induced conformational changes in CXCR4 homo- and heterodimers. J Biol Chem 2005; 280:9895-903. [PMID: 15632118 DOI: 10.1074/jbc.m411151200] [Citation(s) in RCA: 204] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Homo- and heterodimerization have emerged as prominent features of G-protein-coupled receptors with possible impact on the regulation of their activity. Using a sensitive bioluminescence resonance energy transfer system, we investigated the formation of CXCR4 and CCR2 chemokine receptor dimers. We found that both receptors exist as constitutive homo- and heterodimers and that ligands induce conformational changes within the pre-formed dimers without promoting receptor dimer formation or disassembly. Ligands with different intrinsic efficacies yielded distinct bioluminescence resonance energy transfer modulations, indicating the stabilization of distinct receptor conformations. We also found that peptides derived from the transmembrane domains of CXCR4 inhibited activation of this receptor by blocking the ligand-induced conformational transitions of the dimer. Taken together, our data support a model in which chemokine receptor homo- and heterodimers form spontaneously and respond to ligand binding as units that undergo conformational changes involving both protomers even when only one of the two ligand binding sites is occupied.
Collapse
Affiliation(s)
- Yann Percherancier
- Department of Biochemistry, Université de Montréal, Montréal H3C 3J7, Québéc, Canada
| | | | | | | | | | | | | | | |
Collapse
|
16
|
Bakker RA, Dees G, Carrillo JJ, Booth RG, López-Gimenez JF, Milligan G, Strange PG, Leurs R. Domain swapping in the human histamine H1 receptor. J Pharmacol Exp Ther 2004; 311:131-8. [PMID: 15159444 DOI: 10.1124/jpet.104.067041] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
G-protein-coupled receptors (GPCRs) represent the largest family of receptors involved in transmembrane signaling. Although these receptors were generally believed to be monomeric entities, accumulating evidence supports the presence of GPCRs in multimeric forms. Here, using immunoprecipitation as well as time-resolved fluorescence resonance energy transfer to assess protein-protein interactions in living cells, we unambiguously demonstrate the occurrence of dimerization of the human histamine H(1) receptor. We also show the presence of domain-swapped H(1) receptor dimers in which there is the reciprocal exchange of transmembrane domain TM domains 6 and 7 between the receptors present in the dimer. Mutation of aspartate(107) in transmembrane (TM) 3 or phenylalanine(432) in TM6 to alanine results in two radioligand-binding-deficient mutant H(1) receptors. Coexpression of H(1)D(107) A and H(1)F(432)A, however, results in a reconstituted radioligand binding site that exhibits a pharmacological profile that corresponds to the wild-type H(1) receptor. Interestingly, the H(1) receptor radioligands [(3)H]mepyramine and [(3)H]-(-)-trans-1-phenyl-3-N,N-dimethylamino-1,2,3,4-tetrahydronaphthalene show differential saturation binding values (B(max)) for wild-type H(1) receptors but not for the radioligand binding site that is formed upon coexpression of H(1) D(107)A and H(1) F(432)A receptors, suggesting the presence of different H(1) receptor populations.
Collapse
Affiliation(s)
- Remko A Bakker
- Leiden/Amsterdam Center for Drug Research, Faculty of Sciences, Department of Medicinal Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
| | | | | | | | | | | | | | | |
Collapse
|