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Fusion with Promiscuous Gα 16 Subunit Reveals Signaling Bias at Muscarinic Receptors. Int J Mol Sci 2021; 22:ijms221810089. [PMID: 34576254 PMCID: PMC8469978 DOI: 10.3390/ijms221810089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 09/06/2021] [Accepted: 09/14/2021] [Indexed: 11/25/2022] Open
Abstract
A complex evaluation of agonist bias at G-protein coupled receptors at the level of G-protein classes and isoforms including non-preferential ones is essential for advanced agonist screening and drug development. Molecular crosstalk in downstream signaling and a lack of sufficiently sensitive and selective methods to study direct coupling with G-protein of interest complicates this analysis. We performed binding and functional analysis of 11 structurally different agonists on prepared fusion proteins of individual subtypes of muscarinic receptors and non-canonical promiscuous α-subunit of G16 protein to study agonist bias. We have demonstrated that fusion of muscarinic receptors with Gα16 limits access of other competitive Gα subunits to the receptor, and thus enables us to study activation of Gα16 mediated pathway more specifically. Our data demonstrated agonist-specific activation of G16 pathway among individual subtypes of muscarinic receptors and revealed signaling bias of oxotremorine towards Gα16 pathway at the M2 receptor and at the same time impaired Gα16 signaling of iperoxo at M5 receptors. Our data have shown that fusion proteins of muscarinic receptors with α-subunit of G-proteins can serve as a suitable tool for studying agonist bias, especially at non-preferential pathways.
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2
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Shivnaraine RV, Fernandes DD, Ji H, Li Y, Kelly B, Zhang Z, Han YR, Huang F, Sankar KS, Dubins DN, Rocheleau JV, Wells JW, Gradinaru CC. Single-Molecule Analysis of the Supramolecular Organization of the M2 Muscarinic Receptor and the Gαi1 Protein. J Am Chem Soc 2016; 138:11583-98. [DOI: 10.1021/jacs.6b04032] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Rabindra V. Shivnaraine
- Department
of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
| | - Dennis D. Fernandes
- Department
of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
- Department of Chemical & Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Huiqiao Ji
- Department
of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
| | - Yuchong Li
- Department
of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
- Department of Chemical & Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Brendan Kelly
- Department
of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
- Krembil Research
Institute, University Health Network, Toronto, Ontario M5T 2S8, Canada
| | - Zhenfu Zhang
- Department
of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
- Department of Chemical & Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Yi Rang Han
- Department
of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
| | - Fei Huang
- Department
of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
| | - Krishana S. Sankar
- Department
of Physiology, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - David N. Dubins
- Department
of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
| | - Jonathan V. Rocheleau
- Department
of Physiology, University of Toronto, Toronto, Ontario M5G 1L7, Canada
- Institute
of Biomedical and Biomaterial Engineering, University of Toronto, Toronto, Ontario M5S 3G9, Canada
| | - James W. Wells
- Department
of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
| | - Claudiu C. Gradinaru
- Department
of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
- Department of Chemical & Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
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3
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Redka DS, Heerklotz H, Wells JW. Efficacy as an Intrinsic Property of the M2 Muscarinic Receptor in Its Tetrameric State. Biochemistry 2013; 52:7405-27. [DOI: 10.1021/bi4003869] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Dar’ya S. Redka
- Department of Pharmaceutical
Sciences,
Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada M5S 3M2
| | - Heiko Heerklotz
- Department of Pharmaceutical
Sciences,
Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada M5S 3M2
| | - James W. Wells
- Department of Pharmaceutical
Sciences,
Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada M5S 3M2
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4
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Shivnaraine RV, Huang XP, Seidenberg M, Ellis J, Wells JW. Heterotropic cooperativity within and between protomers of an oligomeric M(2) muscarinic receptor. Biochemistry 2012; 51:4518-40. [PMID: 22551249 DOI: 10.1021/bi3000287] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
At least four allosteric sites have been found to mediate the dose-dependent effects of gallamine on the binding of [(3)H]quinuclidinylbenzilate (QNB) and N-[(3)H]methylscopolamine (NMS) to M(2) muscarinic receptors in membranes and solubilized preparations from porcine atria, CHO cells, and Sf9 cells. The rate of dissociation of [(3)H]QNB was affected in a bell-shaped manner with at least one Hill coefficient (n(H)) greater than 1, indicating that at least three allosteric sites are involved. The level of binding of [(3)H]QNB was decreased in a biphasic manner, revealing at least two allosteric sites; binding of [(3)H]NMS was affected in a triphasic, serpentine manner, revealing at least three sites, and values of n(H) >1 pointed to at least four sites. Several lines of evidence indicate that all effects of gallamine were allosteric in nature and could be observed at equilibrium. The rates of equilibration and dissociation suggest that the receptor was predominately oligomeric, and the heterogeneity revealed by gallamine can be attributed to differences in its affinity for the constituent protomers of a tetramer. Those differences appear to arise from inter- and intramolecular cooperativity between gallamine and the radioligand.
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Affiliation(s)
- Rabindra V Shivnaraine
- Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario, Canada M5S 3M2
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5
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Ma AWS, Dong JY, Ma D, Wells JW. Cleavage-resistant fusion proteins of the M(2) muscarinic receptor and Gα(i1). Homotropic and heterotropic effects in the binding of ligands. Biochim Biophys Acta Gen Subj 2011; 1810:592-602. [PMID: 21397664 DOI: 10.1016/j.bbagen.2011.03.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 01/28/2011] [Accepted: 03/02/2011] [Indexed: 11/30/2022]
Abstract
BACKGROUND G protein-coupled receptors fused to a Gα-subunit are functionally similar to their unfused counterparts. They offer an intriguing view into the nature of the receptor-G protein complex, but their usefulness depends upon the stability of the fusion. METHODS Fusion proteins of the M(2) muscarinic receptor and the α-subunit of G(i1) were expressed in CHO and Sf9 cells, extracted in digitonin-cholate, and examined for their binding properties and their electrophoretic mobility on western blots. RESULTS Receptor fused to native α(i1) underwent proteolysis near the point of fusion to release a fragment with the mobility of α(i1). The cleavage was prevented by truncation of the α-subunit at position 18. Binding of the agonist oxotremorine-M to the stable fusion protein from Sf9 cells was biphasic, and guanylylimidodiphosphate promoted an apparent interconversion of sites from higher to lower affinity. With receptor from CHO cells, the apparent capacity for N-[(3)H]methylscopolamine was 60% of that for [(3)H]quinuclidinylbenzilate; binding at saturating concentrations of the latter was inhibited in a noncompetitive manner at low concentrations of unlabeled N-methylscopolamine. CONCLUSIONS A stable fusion protein of the M(2) receptor and truncated α(i1) resembles the native receptor-G protein complex with respect to the guanyl nucleotide-sensitive binding of agonists and the noncompetitive binding of antagonists. GENERAL SIGNIFICANCE Release of the α-subunit is likely to occur with other such fusion proteins, rendering the data ambiguous or misleading. The properties of a chemically stable fusion protein support the notion that signaling proceeds via a stable multimeric complex of receptor and G protein.
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Affiliation(s)
- Amy W-S Ma
- Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario, Canada
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6
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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.
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Suga H, Haga T. Ligand screening system using fusion proteins of G protein-coupled receptors with G protein alpha subunits. Neurochem Int 2007; 51:140-64. [PMID: 17659814 DOI: 10.1016/j.neuint.2007.06.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2007] [Revised: 06/07/2007] [Accepted: 06/08/2007] [Indexed: 01/04/2023]
Abstract
G protein-coupled receptors (GPCRs) constitute one of the largest families of genes in the human genome, and are the largest targets for drug development. Although a large number of GPCR genes have recently been identified, ligands have not yet been identified for many of them. Various assay systems have been employed to identify ligands for orphan GPCRs, but there is still no simple and general method to screen for ligands of such GPCRs, particularly of G(i)-coupled receptors. We have examined whether fusion proteins of GPCRs with G protein alpha subunit (Galpha) could be utilized for ligand screening and showed that the fusion proteins provide an effective method for the purpose. This article focuses on the followings: (1) characterization of GPCR genes and GPCRs, (2) identification of ligands for orphan GPCRs, (3) characterization of GPCR-Galpha fusion proteins, and (4) identification of ligands for orphan GPCRs using GPCR-Galpha fusion proteins.
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Affiliation(s)
- Hinako Suga
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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Park PSH, Wells JW. Monomers and Oligomers of the M2 Muscarinic Cholinergic Receptor Purified from Sf9 Cells. Biochemistry 2003; 42:12960-71. [PMID: 14596611 DOI: 10.1021/bi034491m] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
G protein-coupled receptors are known to form oligomers. To probe the nature of such aggregates, as well as the role and prevalence of monomers, epitope-tagged forms of the M(2) muscarinic receptor have been isolated as oligomers and monomers from Sf9 cells. Membranes from cells coexpressing the c-Myc- and FLAG-tagged receptor were solubilized in digitonin-cholate, and the receptor was purified by successive passage through DEAE-Sepharose, the affinity resin 3-(2'-aminobenzhydryloxy)tropane (ABT)-Sepharose, and hydroxyapatite. Coimmunoprecipitation of the two epitopes indicated the presence of oligomers at each stage of the purification up to but not including the fraction eluted specifically from ABT-Sepharose. The affinity-purified receptor therefore appeared to be monomeric. The failure to detect coimmunoprecipitation was not due to an ineffective antibody, nor did the conditions of purification appear to promote disaggregation. Receptor at all stages of purification bound N-[(3)H]methylscopolamine and [(3)H]quinuclidinylbenzilate with high affinity, but the capacity of receptors that were not retained on ABT-Sepharose was only 4% of that expected from densitometry of western blots probed with an anti-M(2) antibody. Similarly low activity was found with oligomers isolated by successive passage of coexpressed receptor on anti-c-Myc and anti-FLAG immunoaffinity columns. M(2) muscarinic receptors therefore appear to coexist as active monomers and largely or wholly inactive oligomers in solubilized extracts of Sf9 cells. A different pattern emerged when coinfected cells were treated with quinuclidinylbenzilate prior to solubilization, in that ABT-purified receptors from those cells exhibited coimmunoprecipitation. Treatment with the antagonist therefore led to oligomers in which at least some of the constituent sites were active and were retained by ABT-Sepharose.
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Affiliation(s)
- Paul S-H Park
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada M5S 2S2
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9
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Mosser VA, Amana IJ, Schimerlik MI. Kinetic analysis of M2 muscarinic receptor activation of Gi in Sf9 insect cell membranes. J Biol Chem 2002; 277:922-31. [PMID: 11689554 DOI: 10.1074/jbc.m104210200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A steady-state kinetic mechanism describing the interaction of M(2) muscarinic acetylcholine receptors and the guanine nucleotide-binding protein G(i)alpha(2)beta(1)gamma(3) are presented. Data are consistent with two parallel pathways of agonist-promoted GTPase activity arising from receptor coupled to a single or multiple guanine nucleotide-binding proteins. An aspartate 103 to asparagine receptor mutation resulted in a receptor lacking the ability to catalyze the binding of guanosine-5'-O-(3-thiotriphosphate) or guanosine triphosphate hydrolysis by the G protein. An aspartate 69 to asparagine receptor mutant was able to catalyze agonist-specific guanine nucleotide exchange and GTPase activity. A threonine 187 to alanine receptor mutation resulted in a receptor that catalyzed guanine nucleotide exchange comparable with wild-type receptors but had reduced ability to stimulate GTP hydrolysis. A tyrosine 403 to phenylalanine receptor mutation resulted in an increase in agonist-promoted GTPAse activity compared with wild type. The observation that the threonine 187 and tyrosine 403 mutants promote guanine nucleotide exchange similarly to wild type but alter GTPase activity compared with wild type suggests that the effects of the mutations arise downstream from guanine nucleotide exchange and may result from changes in receptor-G protein dissociation.
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Affiliation(s)
- Valerie A Mosser
- Department of Biochemistry and Biophysics and the Environmental Health Sciences Center, Oregon State University, Corvallis, Oregon 97331-7305, USA
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10
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Heitz F, Holzwarth JA, Gies JP, Pruss RM, Trumpp-Kallmeyer S, Hibert MF, Guenet C. Site-directed mutagenesis of the putative human muscarinic M2 receptor binding site. Eur J Pharmacol 1999; 380:183-95. [PMID: 10513578 DOI: 10.1016/s0014-2999(99)00439-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Experimental probing of the model of the muscarinic M2 receptor binding site proposed by Hibert et al. [Hibert, M.F., Trumpp-Kallmeyer, S., Bruinsvels, A., Hoflak, K., 1991. Three-dimensional models of neurotransmitter G-binding protein-coupled receptors. Mol. Pharmacol. 40, 8-15.] was achieved by mutating each amino-acid proposed to interact with muscarinic ligands. Pharmacological analysis of the different mutant receptors transiently expressed in human embryonic kidney (HEK/293) cells was performed with a variety of agonists and antagonists. D103A, Y403A and N404A mutations prevented binding of [3H] N-methylscopolamine and [3H] quinuclidinyl benzilate with a reduction in affinity greater than 100-fold, indicating essential contributions of these residues to the binding site for the radioligands. W400A and W155A mutations had very large effects on the binding of [3H] N-methylscopolamine (150-fold, 960-fold) but modest effects on the binding of [3H] quinuclidinyl benzilate (4-fold, 17-fold). In addition, binding of oxotremorine-M, oxotremorine, arecoline and pilocarpine to W155A resulted in a greater than 100-fold decrease in affinity. Threonine mutations (T187A and T190A) alter binding of most agonists but not of antagonists. W99 makes little contribution (< 10-fold) to the binding site of the M2 receptor. D103, W155, W400, Y403 and N404 are likely to be part of the binding site for N-methylscopolamine and also to contribute to the binding site for quinuclidinyl benzilate. Some of the predicted residues do not seem to be part of the M2 receptor binding site but W155 is important for proper ligand binding on the muscarinic M2 receptor, as predicted by the proposed model.
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Affiliation(s)
- F Heitz
- Marion Merrell Research Institute, Strasbourg, France
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11
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Lachance M, Ethier N, Wolbring G, Schnetkamp PP, Hébert TE. Stable association of G proteins with beta 2AR is independent of the state of receptor activation. Cell Signal 1999; 11:523-33. [PMID: 10405763 DOI: 10.1016/s0898-6568(99)00024-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
beta 2-Adrenergic receptors expressed in Sf9 cells activate endogenous Gs and adenylyl cyclase [Mouillac B., Caron M., Bonin H., Dennis M. and Bouvier M. (1992) J. Biol. Chem. 267, 21733-21737]. However, high affinity agonist binding is not detectable under these conditions suggesting an improper stoichiometry between the receptor and the G protein and possibly the effector molecule as well. In this study we demonstrate that when beta 2-adrenergic receptors were co-expressed with various mammalian G protein subunits in Sf9 cells using recombinant baculoviruses signalling properties found in native receptor systems were reconstituted. For example, when beta 2AR was co-expressed with the Gs alpha subunit, maximal receptor-mediated adenylyl cyclase stimulation was greatly enhanced (60 +/- 9.0 versus 150 +/- 52 pmol cAMP/min/mg protein) and high affinity, GppNHp-sensitive, agonist binding was detected. When G beta gamma subunits were co-expressed with Gs alpha and the beta 2AR, receptor-stimulated GTPase activity was also demonstrated, in contrast to when the receptor was expressed alone, and this activity was higher than when beta 2AR was co-expressed with Gs alpha alone. Other properties of the receptor, including receptor desensitization and response to inverse agonists were unaltered. Using antisera against an epitope-tagged beta 2AR, both Gs alpha and beta gamma subunits could be co-immunoprecipitated with the beta 2AR under conditions where subunit dissociation would be expected given current models of G protein function. A desensitization-defective beta 2AR (S261, 262, 345, 346A) and a mutant which is constitutively desensitized (C341G) could also co-immunoprecipitate G protein subunits. These results will be discussed in terms of a revised view of G protein-mediated signalling which may help address issues of specificity in receptor/G protein coupling.
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Affiliation(s)
- M Lachance
- Centre de Recherche, Institut de Cardiologie de Montréal, PQ, Canada
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12
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Beukers MW, Klaassen CH, De Grip WJ, Verzijl D, Timmerman H, Leurs R. Heterologous expression of rat epitope-tagged histamine H2 receptors in insect Sf9 cells. Br J Pharmacol 1997; 122:867-74. [PMID: 9384502 PMCID: PMC1565019 DOI: 10.1038/sj.bjp.0701466] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
1. Rat histamine H2 receptors were epitope-tagged with six histidine residues at the C-terminus to allow immunological detection of the receptor. Recombinant baculoviruses containing the epitope-tagged H2 receptor were prepared and were used to infect insect Sf9 cells. 2. The His-tagged H2 receptors expressed in insect Sf9 cells showed typical H2 receptor characteristics as determined with [125I]-aminopotentidine (APT) binding studies. 3. In Sf9 cells expressing the His-tagged H2 receptor histamine was able to stimulate cyclic AMP production 9 fold (EC50=2.1+/-0.1 microM) by use of the endogenous signalling pathway. The classical antagonists cimetidine, ranitidine and tiotidine inhibited histamine induced cyclic AMP production with Ki values of 0.60+/-0.43 microM, 0.25+/-0.15 microM and 28+/-7 nM, respectively (mean+/-s.e.mean, n=3). 4. The expression of the His-tagged H2 receptors in infected Sf9 cells reached functional levels of 6.6+/-0.6 pmol mg(-1) protein (mean+/-s.e.mean, n=3) after 3 days of infection. This represents about 2 x 10(6) copies of receptor/cell. Preincubation of the cells with 0.03 mM cholesterol-beta-cyclodextrin complex resulted in an increase of [125I]-APT binding up to 169+/-5% (mean+/-s.e.mean, n=3). 5. The addition of 0.03 mM cholesterol-beta-cyclodextrin complex did not affect histamine-induced cyclic AMP production. The EC50 value of histamine was 3.1+/-1.7 microM in the absence of cholesterol-beta-cyclodextrin complex and 11.1+/-5.5 microM in the presence of cholesterol-beta-cyclodextrin complex (mean+/-s.e.mean, n=3). Also, the amount of cyclic AMP produced in the presence of 100 microM histamine was identical, 85+/-18 pmol/10(6) cells in the absence and 81+/-11 pmol/10(6) cells in the presence of 0.03 mM cholesterol-beta-cyclodextrin complex (mean+/-s.e.mean, n=3). 6. Immunofluorescence studies with an antibody against the His-tag revealed that the majority of the His-tagged H2 receptors was localized inside the insect Sf9 cells, although plasma membrane labelling could be identified as well. 7. These experiments demonstrate the successful expression of His-tagged histamine H2 receptors in insect Sf9 cells. The H2 receptors couple functionally to the insect cell adenylate cyclase. However, our studies with cholesterol complementation and with immunofluorescent detection of the His-tag reveal that only a limited amount of H2 receptor protein is functional. These functional receptors are targeted to the plasma membrane.
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Affiliation(s)
- M W Beukers
- Leiden/Amsterdam Center for Drug Research, Division of Medicinal Chemistry, Amsterdam, The Netherlands
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13
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Weill C, Autelitano F, Guenet C, Heitz F, Goeldner M, Ilien B. Pharmacological and structural integrity of muscarinic M2 acetylcholine receptors produced in Sf9 insect cells. Eur J Pharmacol 1997; 333:269-78. [PMID: 9314044 DOI: 10.1016/s0014-2999(97)01139-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Muscarinic acetylcholine receptors (human m2 subtype), expressed in Sf9 cells, using the baculovirus system, were purified and found to display the expected ligand binding properties, whether membrane-bound or affinity-purified. The purified recombinant receptors were specifically photolabelled with p-N,N-[3H]dimethylamino and p-N,N-[3H]dibutylamino benzene diazonium derivatives. Electrophoretic patterns for covalent radioactive incorporation of the probes were essentially similar to those for [3H]propylbenzilylcholine mustard-labelled receptor sites but were dependent on the infection time of Sf9 cells. Pharmacological properties of the recombinant receptors being unaltered did not reflect structural integrity of the protein as substantial proteolytic fragmentation was detected at a prolonged infection time, i.e., at the highest level of expression. Selection of overexpression conditions, as illustrated here for muscarinic receptors, thus requires not only pharmacological controls, but also analysis of the covalently labelled protein under strongly dissociating conditions.
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Affiliation(s)
- C Weill
- Laboratoire de Chimie Bio-Organique, U.R.A. 1386 C.N.R.S., Faculté de Pharmacie, Université Louis Pasteur, Illkirch, France
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14
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Massotte D, Baroche L, Simonin F, Yu L, Kieffer B, Pattus F. Characterization of delta, kappa, and mu human opioid receptors overexpressed in baculovirus-infected insect cells. J Biol Chem 1997; 272:19987-92. [PMID: 9242668 DOI: 10.1074/jbc.272.32.19987] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The cDNAs encoding human delta (hDOR), kappa (hKOR) and micro (hMOR) opioid receptors were cloned in the baculovirus Autographa californica (AcMNPV) under the control of the polyhedrin promoter with or without an amino-terminal hexahistidine tag. Expression levels were optimized in Spodoptera frugiperda (Sf9) cells and were in the following order hMOR > hDOR > hKOR. The receptors bound antagonists with affinity values similar to those published previously for the receptors expressed in mammalian cells. They also retained selectivity toward specific antagonists. The three receptors bound peptidic agonists with low affinity, suggesting that they might not be functionally coupled to intracellular effectors. Introduction of an amino-terminal hexahistidine tag decreased the levels of expression markedly. Only hMOR-his was expressed at a level allowing binding study, but no difference could be detected in the affinities of both agonists and antagonists compared with the nontagged protein. hMOR expression was also optimized in High Five cells leading to a further increase in protein production. The pharmacological profile was similar to the one obtained when the receptor was expressed in Sf9 cells. Our results show that the baculovirus expression system is suitable for large scale production of human opioid receptors.
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MESH Headings
- Analgesics, Opioid/metabolism
- Animals
- Baculoviridae
- Cells, Cultured
- Cloning, Molecular
- Diprenorphine/metabolism
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
- Enkephalins/metabolism
- Gene Expression
- Humans
- Kinetics
- Ligands
- Narcotic Antagonists/metabolism
- Oligopeptides/metabolism
- Opioid Peptides
- Receptors, Opioid, delta/genetics
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, kappa/genetics
- Receptors, Opioid, kappa/metabolism
- Receptors, Opioid, mu/genetics
- Receptors, Opioid, mu/metabolism
- Recombinant Proteins/metabolism
- Spodoptera
- Transfection
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Affiliation(s)
- D Massotte
- Département des Récepteurs et Protéines membranaires, CNRS Unité Propre de Recherche 9050, F-64700 Illkirch-Graffenstaden, France.
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Heitz F, Nay C, Guenet C. Expression of functional human muscarinic M2 receptors in different insect cell lines. J Recept Signal Transduct Res 1997; 17:305-17. [PMID: 9029498 DOI: 10.3109/10799899709036611] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Human M2 receptors were expressed using the baculovirus expression system in three different insect cell lines: Sf9, Sf21 and High5. The level of expression was slightly increased in Sf21 cells versus Sf9 cells. In contrast, High5 cells were not able to produce more recombinant protein than Sf9. We also show that in both Spodoptera frugiperda cell lines a peak of expression was reached after 6 days of infection, whereas in High5 cells, the maximum of expression occurred after 3 days. Immunodetection of m2 muscarinic receptor clearly shows that the expressed protein undergoes significant proteolysis in both the Sf9 and High5 cells, whereas in the Sf21 cells this phenomenon was less detectable. Additionally, we show that in all three cell lines, the expressed recombinant receptor was functional in that it was able to stimulate GTP gamma S binding in the presence of exogenous G-proteins. Analysis of the population of G-proteins (G alpha i, G alpha o and G beta common) in Sf21 and High5 cells is provided.
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Affiliation(s)
- F Heitz
- Marion Merrell Research Institute, Strasbourg, France
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