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Chazot PL, Strange PG. Importance of thiol groups in ligand binding to D2 dopamine receptors from brain and anterior pituitary gland. Biochem J 1992; 281 ( Pt 2):377-80. [PMID: 1736887 PMCID: PMC1130694 DOI: 10.1042/bj2810377] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The effects of the thiol group reagent 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) on D2 dopamine receptors have been examined in three brain regions (caudate nucleus, putamen and olfactory tubercle), and in the anterior and neurointermediate lobes of the pituitary gland. Whereas the receptors in brain were insensitive to DTNB, a dose-dependent inhibition of [3H]spiperone binding to D2 receptors in both lobes of the pituitary gland was observed. The effects in the pituitary could be reversed by subsequent treatment with dithiothreitol and could be prevented by prior occupancy of the receptor binding site with a ligand. The effect of DTNB was to decrease the number of ligand-binding sites without altering the affinity of those remaining. The results show that modification of a thiol group of the D2 dopamine receptor in the two lobes of the pituitary gland tested here significantly affects ligand binding. There is therefore a difference between the D2 dopamine receptor populations in brain and pituitary in their sensitivity to modification by DTNB, and this may imply the existence of different receptor isoforms in the two issues.
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Chazot JA, Strange PG. Coupling of D2 dopamine receptors to G-proteins in solubilized preparations of bovine caudate nucleus. Biochem J 1992; 281 ( Pt 2):369-75. [PMID: 1736886 PMCID: PMC1130693 DOI: 10.1042/bj2810369] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
1. The coupling of D2 dopamine receptors and G-proteins has been examined in cholate-solubilized preparations of bovine caudate nucleus. 2. No receptor-G-protein coupling could be detected in solubilized preparations obtained in 0.3% cholate, but if this preparation is diluted 5-fold, coupling is re-established. 3. The dilution process was examined, and it was shown that the change in ionic strength was an important factor in modulating the observed receptor-G-protein interaction. 4. Ionic strength was shown, however, not to be the primary determinant of receptor-G-protein coupling. This is likely to be the formation, upon dilution of the preparation, of vesicles in which receptor and G-protein reassociate. 5. The formation of vesicles upon dilution was examined by a variety of techniques, including thermal-stability studies, gel filtration, centrifugation and electron microscopy.
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Hayter PM, Curling EM, Baines AJ, Jenkins N, Salmon I, Strange PG, Bull AT. Chinese hamster ovary cell growth and interferon production kinetics in stirred batch culture. Appl Microbiol Biotechnol 1991; 34:559-64. [PMID: 1367524 DOI: 10.1007/bf00167898] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Recombinant human interferon-gamma production by Chinese hamster ovary cells was restricted to the growth phase of batch cultures in serum-free medium. The specific interferon production rate was highest during the initial period of exponential growth but declined subsequently in parallel with specific growth rate. This decline in specific growth rate and interferon productivity was associated with a decline in specific metabolic activity as determined by the rate of glucose uptake and the rates of lactate and ammonia production. The ammonia and lactate concentrations that had accumulated by the end of the batch culture were not inhibitory to growth. Glucose was exhausted by the end of the growth phase but increased glucose concentrations did not improve the cell yield or interferon production kinetics. Analysis of amino acid metabolism showed that glutamine and asparagine were exhausted by the end of the growth phase, but supplementation of these amino acids did not improve either cell or product yields. When glutamine was omitted from the growth medium there was no cell proliferation but interferon production occurred, suggesting that recombinant protein production can be uncoupled from cell proliferation.
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Chazot PL, Wilkins M, Strange PG. Site-specific antibodies as probes of the structure and function of the brain D2 dopamine receptor. Biochem Soc Trans 1991; 19:143S. [PMID: 1716218 DOI: 10.1042/bst019143s] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Murray DC, Mosley M, Strange PG. Muscarinic acetylcholine receptors in the lung. Biochem Soc Trans 1991; 19:145S. [PMID: 1889540 DOI: 10.1042/bst019145s] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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83
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Newman-Tancredi A, Strange PG. High level expression of serotonin (5HT-1a) receptor in animal cells. Biochem Soc Trans 1991; 19:144S. [PMID: 1832392 DOI: 10.1042/bst019144s] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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84
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Hollis CM, Strange PG. Chemical modification of the D1 dopamine receptor from bovine brain. Biochem Soc Trans 1991; 19:142S. [PMID: 1832391 DOI: 10.1042/bst019142s] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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85
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Abstract
Advances in techniques for cloning neurotransmitter receptors have revealed new targets for selective drug design. Cell systems for more efficient expression of cloned receptor genes have also been developed. Knowledge of the nature of ligand-binding sites is now becoming available and this should aid in the design of better drugs with fewer side effects.
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Presland JP, Strange PG. pH dependence of sulpiride binding to D2 dopamine receptors in bovine brain. Biochem Pharmacol 1991; 41:R9-12. [PMID: 1826198 DOI: 10.1016/0006-2952(91)90187-a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In summary then these data suggest that butyrophenones such as spiperone and substituted benzamides such as sulpiride interact with different groups at the active site of the D2 dopamine receptor. The drugs bind in different modes to the receptor which must therefore contain separate but overlapping binding sites for the two classes of drug. Understanding the precise interactions involved that generate this selectivity will be important for drug design.
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Curling EM, Hayter PM, Baines AJ, Bull AT, Gull K, Strange PG, Jenkins N. Recombinant human interferon-gamma. Differences in glycosylation and proteolytic processing lead to heterogeneity in batch culture. Biochem J 1990; 272:333-7. [PMID: 2125204 PMCID: PMC1149704 DOI: 10.1042/bj2720333] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Recombinant human interferon-gamma (Hu-IFN-gamma) produced by Chinese-hamster ovary (CHO) cells was analysed by immunoprecipitation and SDS/PAGE. Up to twelve molecular-mass variants were secreted by this cell line. Three variants were recovered after enzymic removal of all N-linked oligosaccharides or when glycosylation was inhibited by tunicamycin. The presence of three polypeptide forms rather than a single form suggested that proteolytic cleavage had occurred at two sites in both the glycosylated and non-glycosylated forms. Proteolytically cleaved IFN-gamma was more prevalent in cell lysates than in the secreted glycoprotein. In common with naturally produced IFN-gamma, both fully glycosylated IFN-gamma (asparagine residues 28 and 100 occupied) and partially glycosylated product (thought to be substituted at position Asn28) were secreted. This was deduced from the Mr of the glycosylated products and the relative amounts of sialic acid expressed by each variant. In contrast with naturally produced IFN-gamma, non-glycosylated IFN-gamma was also secreted by the transfected CHO cells. When the cells were grown in batch culture in serum-free medium under pH and dissolved-oxygen control, the proportion of non-glycosylated IFN-gamma increased from 3 to 5% after 3 h, to 30% of the total IFN-gamma present after 195 h. This change in the proportion of glycosylated protein produced was not seen when metabolically labelled IFN-gamma was incubated for 96 h with cell-free supernatant from actively growing CHO cells. This implied that an alteration in intracellular glycosylation was occurring rather than a degradation of oligosaccharide side chains after secretion. The decrease in IFN-gamma glycosylation was independent of the glucose concentration in the culture medium, but could be related to specific growth and IFN-gamma production rates, as these declined steadily after 50 h of culture, in line with the increased production of non-glycosylated IFN-gamma.
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Williamson RA, Strange PG. Evidence for the importance of a carboxyl group in the binding of ligands to the D2 dopamine receptor. J Neurochem 1990; 55:1357-65. [PMID: 2144583 DOI: 10.1111/j.1471-4159.1990.tb03147.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A series of group specific modifying reagents were tested for their effects on [3H]spiperone binding to brain D2 dopamine receptors to identify amino acid residues at the binding site of the D2 dopamine receptor that are critical for ligand binding. The dependence of ligand binding to the receptor on the pH of the incubation medium was also examined. N-Acetylimidazole, 5,5'-dithiobis(2-nitrobenzoic acid), 1,2-cyclohexanedione, and acetic anhydride had no specific effect on [3H]spiperone binding, indicating the lack of participation of tyrosine, free sulphydryl, arginine, or primary amino groups in ligand binding to the receptor. N,N'-Dicyclohexylcarbodiimide (DCCD) potently reduced the number of [3H]spiperone binding sites, indicating that a carboxyl group is involved in ligand binding to the receptor. The effects of DCCD could be prevented by prior incubation of the receptor with D2 dopamine receptor selective compounds. The pH-binding profile for [3H]spiperone binding indicated the importance of an ionising group of pKa 5.2 for ligand binding which may be the same carboxyl group. Diethyl pyrocarbonate, the histidine modifying reagent, also inhibited [3H]spiperone binding, reducing the affinity of the receptor for this ligand but the effects were not at the ligand binding site. From the effects of pH changes on ligand binding some evidence was obtained for a second ionising group (pKa 7.0) that specifically affects the binding of substituted benzamide drugs to the receptor. It is concluded that the D2 dopamine receptor binding site contains separate but over-lapping binding regions for antagonists such as spiperone and substituted benzamide drugs. The former region contains an important carboxyl group; the latter region contains another group that may be a second carboxyl group or a histidine.
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Abstract
Significant new information on the D2 dopamine receptor has recently become available from a combination of protein chemical and molecular genetic analyses. Molecular genetic studies have shown the receptor to be a member of the family of receptors that are linked to G proteins and that have structures predicted to contain seven transmembrane domains. Two distinct species of D2 dopamine receptor have been found which may differ in their coupling to G proteins; their distributions have been mapped at the nucleic acid level. The D2 dopamine receptor has been purified from brain and anterior pituitary and characterized. Chemical modification of the brain receptor provides evidence for the importance of a carboxyl group that interacts with ligands at the receptor binding site. Here, Philip Strange discusses these points and proposes models of receptor-ligand interaction based on the conservation of several aspartic acid residues in receptors that bind cationic amines.
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Chazot JA, Strange PG. Characterization of D2-dopamine receptor-G-protein interaction in solubilized preparations. Biochem Soc Trans 1990; 18:431. [PMID: 2142651 DOI: 10.1042/bst0180431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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95
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Chazot PL, Strange PG. Comparison of purified D2-dopamine receptor from bovine brain and pituitary gland. Biochem Soc Trans 1990; 18:432. [PMID: 2142652 DOI: 10.1042/bst0180432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Strange PG. States and subtypes of the 5-HT2 serotonin receptor: interpretation of the data. J Neurochem 1990; 54:1085-6. [PMID: 2303808 DOI: 10.1111/j.1471-4159.1990.tb02364.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Abstract
D2 dopamine receptors have been extracted from bovine brain using the detergent cholate and purified approximately 20,000-fold by affinity chromatography on haloperidol-sepharose and wheat germ agglutinin-agarose columns. The purified preparation contains D2 dopamine receptors as judged by the pharmacological specificity of [3H]spiperone binding to the purified material. The sp. act. of [3H]spiperone binding in the purified preparation is 2.5 nmol/mg protein. The purified preparation shows a major diffuse band at Mr 95,000 upon SDS-polyacrylamide gel electrophoresis and there is evidence for microheterogeneity either at the protein or glycosylation level. Photoaffinity labelling of D2 dopamine receptors also shows a species of Mr 95,000. The D2 dopamine receptor therefore is a glycoprotein of Mr 95,000.
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Leonard MN, Halliday CA, Marriott AS, Strange PG. D2 dopamine receptors in rat striatum are homogeneous as revealed by ligand-binding studies. Biochem Pharmacol 1988; 37:4335-9. [PMID: 3196358 DOI: 10.1016/0006-2952(88)90615-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
D2 dopamine receptors in rat striatum have been analysed using the binding of [3H]domperidone. Competition experiments were performed with classical dopamine antagonists and antagonists reported by other workers to discriminate D2 dopamine receptor sub-classes. In all cases competition data conformed to a single binding site interaction so that there is no evidence for heterogeneity of the D2 dopamine receptor.
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Shearman MS, Strange PG. Guanine nucleotide effects on agonist binding to serotonin 5HT2 receptors in rat frontal cortex. Biochem Pharmacol 1988; 37:3097-102. [PMID: 3401241 DOI: 10.1016/0006-2952(88)90306-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Specific [3H]ketanserin binding to serotonin 5-HT2 receptors of rat frontal cortex tissue is of high affinity, saturable and unaffected by guanine nucleotides. Antagonists displace [3H]ketanserin from a single recognition site (pseudo-Hill coefficients close to unity), which is also unaffected by guanine nucleotides. Agonist displacement of either [3H]ketanserin or [3H]spiperone from three different membrane preparations showed pseudo-Hill coefficients less than one, and may be described in terms of two agonist binding sites with differing agonist affinities. In the presence of guanine nucleotides, overall agonist affinity was lowered slightly, with little or no change in pseudo-Hill coefficient.
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