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Biffen M, Matsui H, Edwards S, Leishman AJ, Eiho K, Holness E, Satterthwaite G, Doyle I, Wada H, Fraser NJ, Hawkins SL, Aoki M, Tomizawa H, Benjamin AD, Takaku H, McInally T, Murray CM. Biological characterization of a novel class of toll-like receptor 7 agonists designed to have reduced systemic activity. Br J Pharmacol 2012; 166:573-86. [PMID: 22122192 DOI: 10.1111/j.1476-5381.2011.01790.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND AND PURPOSE Toll-like receptor 7 (TLR7) agonists have potential in the treatment of allergic diseases. However, the therapeutic utility of current low molecular weight TLR7 agonists is limited by their systemic activity, resulting in unwanted side effects. We have developed a series of TLR7-selective 'antedrugs', including SM-324405 and AZ12441970, which contain an ester group rapidly cleaved in plasma to reduce systemic exposure. EXPERIMENTAL APPROACH Agonist activity at TLR7 of the parent ester and acid metabolite was assessed in vitro in reporter cells and primary cells from a number of species. Pharmacokinetics following a dose to the lungs was assessed in mice and efficacy evaluated in vivo with a mouse allergic airway model. KEY RESULTS Compounds were selective agonists for TLR7 with no crossover to TLR8 and were metabolically unstable in plasma with the acid metabolite showing substantially reduced activity in a number of assays. The compounds inhibited IL-5 production and induced IFN-α, which mediated the inhibition of IL-5. When dosed into the lung the compounds were rapidly metabolized and short-term exposure of the 'antedrug' was sufficient to activate the IFN pathway. AZ12441970 showed efficacy in a mouse allergic airway model with minimal induction of systemic IFN-α, consistent with the low plasma levels of compound. CONCLUSIONS AND IMPLICATIONS The biological and metabolic profiles of these TLR7-selective agonist 'antedrug' compounds are consistent with a new class of compound that could be administered locally for the treatment of allergic diseases, while reducing the risk of systemic side effects. LINKED ARTICLE This article is commented on by Kaufman and Jacoby, pp. 569-572 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2011.01758.x.
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Affiliation(s)
- M Biffen
- Department of Bioscience, AstraZeneca R&D Charnwood, Loughborough, Leicestershire, UK
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2
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Matsuzaki S, Zazubovich V, Fraser NJ, Cogdell RJ, Small GJ. Energy Transfer Dynamics in LH2 Complexes of Rhodopseudomonas acidophila Containing Only One B800 Molecule. J Phys Chem B 2001. [DOI: 10.1021/jp0037347] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- S. Matsuzaki
- Ames Laboratory, U.S. Department of Energy and Department of Chemistry, Iowa State University, Ames, Iowa 50011, and Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G128 QQ, United Kingdom
| | - V. Zazubovich
- Ames Laboratory, U.S. Department of Energy and Department of Chemistry, Iowa State University, Ames, Iowa 50011, and Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G128 QQ, United Kingdom
| | - N. J. Fraser
- Ames Laboratory, U.S. Department of Energy and Department of Chemistry, Iowa State University, Ames, Iowa 50011, and Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G128 QQ, United Kingdom
| | - R. J. Cogdell
- Ames Laboratory, U.S. Department of Energy and Department of Chemistry, Iowa State University, Ames, Iowa 50011, and Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G128 QQ, United Kingdom
| | - G. J. Small
- Ames Laboratory, U.S. Department of Energy and Department of Chemistry, Iowa State University, Ames, Iowa 50011, and Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G128 QQ, United Kingdom
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3
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Gall A, Robert B, Cogdell RJ, Bellissent-Funel MC, Fraser NJ. Probing the binding sites of exchanged chlorophyll a in LH2 by Raman and site-selection fluorescence spectroscopies. FEBS Lett 2001; 491:143-7. [PMID: 11226437 DOI: 10.1016/s0014-5793(01)02161-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [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: 11/21/2022]
Abstract
In this work we have selectively released the 800 nm absorbing bacteriochlorophyll a molecules of the LH2 protein from the photosynthetic bacterium Rhodopseudomonas acidophila, strain 10050, and replaced them with chlorophyll a (Chla). A combination of low-temperature electronic absorption, resonance Raman and site-selection fluorescence spectroscopies revealed that the Chla pigments are indeed bound in the B800 binding site; this is the first work that formally proves that such non-native chlorins can be inserted correctly into LH2.
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Affiliation(s)
- A Gall
- Laboratoire Lèon Brillouin (CEA-CNRS), CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France.
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4
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Macpherson AN, Arellano JB, Fraser NJ, Cogdell RJ, Gillbro T. Efficient energy transfer from the carotenoid S(2) state in a photosynthetic light-harvesting complex. Biophys J 2001; 80:923-30. [PMID: 11159459 PMCID: PMC1301290 DOI: 10.1016/s0006-3495(01)76071-7] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.3] [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: 10/21/2022] Open
Abstract
Previously, the spatial arrangement of the carotenoid and bacteriochlorophyll molecules in the peripheral light-harvesting (LH2) complex from Rhodopseudomonas acidophila strain 10050 has been determined at high resolution. Here, we have time resolved the energy transfer steps that occur between the carotenoid's initial excited state and the lowest energy group of bacteriochlorophyll molecules in LH2. These kinetic data, together with the existing structural information, lay the foundation for understanding the detailed mechanisms of energy transfer involved in this fundamental, early reaction in photosynthesis. Remarkably, energy transfer from the rhodopin glucoside S(2) state, which has an intrinsic lifetime of approximately 120 fs, is by far the dominant pathway, with only a minor contribution from the longer-lived S(1) state.
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Affiliation(s)
- A N Macpherson
- Department of Biophysical Chemistry, Umeå University, SE-90187 Umeå, Sweden.
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5
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Abstract
This concise review describes the current status of research into how carotenoids function in bacterial photosynthesis. This is illustrated by reference to very recent studies on both the photoprotective and antenna functions of carotenoids. The major remaining open questions on the detailed molecular mechanisms involved in these reactions are highlighted.
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Affiliation(s)
- N J Fraser
- Division of Biochemistry & Molecular Biology, Davidson Building, IBLS, University of Glasgow, Glasgow, G12 8QQ, UK,
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Herek JL, Fraser NJ, Pullerits T, Martinsson P, Polívka T, Scheer H, Cogdell RJ, Sundström V. B800-->B850 energy transfer mechanism in bacterial LH2 complexes investigated by B800 pigment exchange. Biophys J 2000; 78:2590-6. [PMID: 10777755 PMCID: PMC1300848 DOI: 10.1016/s0006-3495(00)76803-2] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.3] [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: 10/21/2022] Open
Abstract
Femtosecond transient absorption measurements were performed on native and a series of reconstituted LH2 complexes from Rhodopseudomonas acidophila 10050 at room temperature. The reconstituted complexes contain chemically modified tetrapyrrole pigments in place of the native bacteriochlorophyll a-B800 molecules. The spectral characteristics of the modified pigments vary significantly, such that within the B800 binding sites the B800 Q(y) absorption maximum can be shifted incrementally from 800 to 670 nm. As the spectral overlap between the B800 and B850 Q(y) bands decreases, the rate of energy transfer (as determined by the time-dependent bleaching of the B850 absorption band) also decreases; the measured time constants range from 0.9 ps (bacteriochlorophyll a in the B800 sites, Q(y) absorption maximum at 800 nm) to 8.3 ps (chlorophyll a in the B800 sites, Q(y) absorption maximum at 670 nm). This correlation between energy transfer rate and spectral blue-shift of the B800 absorption band is in qualitative agreement with the trend predicted from Förster spectral overlap calculations, although the experimentally determined rates are approximately 5 times faster than those predicted by simulations. This discrepancy is attributed to an underestimation of the electronic coupling between the B800 and B850 molecules.
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Affiliation(s)
- J L Herek
- Department of Chemical Physics, Lund University, S-22100 Lund, Sweden
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7
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Zumpe ET, Tilakaratne N, Fraser NJ, Christopoulos G, Foord SM, Sexton PM. Multiple ramp domains are required for generation of amylin receptor phenotype from the calcitonin receptor gene product. Biochem Biophys Res Commun 2000; 267:368-72. [PMID: 10623626 DOI: 10.1006/bbrc.1999.1943] [Citation(s) in RCA: 61] [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: 11/22/2022]
Abstract
Calcitonin (CT), calcitonin gene-related peptide (CGRP), amylin, and adrenomedullin constitute a family of structurally related peptides that signal via either the calcitonin receptor-like receptor or the CT receptor, with receptor phenotype determined by coexpression of one of the three receptor activity-modifying proteins (RAMPs). The nature of the interaction between the receptor and RAMP was investigated using chimeras between RAMP1 and RAMP2 where the amino-terminal domain of RAMP1 was attached to the transmembrane domain and carboxy terminus of RAMP2 and called RAMP1/2, and vice versa for RAMP2/1. Cotransfection of wild-type or chimeric RAMPs with the insert-negative isoform of the human CT receptor (hCTR(I1-)) into COS-7 cells resulted in the expression of (125)I-rat amylin binding sites. Highest specific binding was observed when either RAMP1 or RAMP2/1 were cotransfected, indicating the importance of the RAMP transmembrane domain and/or carboxy terminus for the degree to which amylin receptors are expressed. In contrast, the phenotype generated was primarily determined by the amino terminus, with similar RAMP1- and RAMP1/2-induced receptor phenotypes that had higher affinity for human CGRPalpha and lower affinity for human calcitonin than the RAMP2- and RAMP2/1-induced receptors.
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Affiliation(s)
- E T Zumpe
- Molecular Pharmacology Laboratory, Department of Pharmacology, University of Melbourne, Victoria, 3010, Australia
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8
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Foord SM, Wise A, Brown J, Main MJ, Fraser NJ. The N-terminus of RAMPs is a critical determinant of the glycosylation state and ligand binding of calcitonin receptor-like receptor. Biochem Soc Trans 1999; 27:535-9. [PMID: 10917636 DOI: 10.1042/bst0270535] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- S M Foord
- Molecular Pharmacology, GlaxoWellcome Medicines Research Centre, Stevenage, Hertfordshire, UK
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9
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Fraser NJ, Dominy PJ, Ucker B, Simonin I, Scheer H, Cogdell RJ. Selective release, removal, and reconstitution of bacteriochlorophyll a molecules into the B800 sites of LH2 complexes from Rhodopseudomonas acidophila 10050. Biochemistry 1999; 38:9684-92. [PMID: 10423247 DOI: 10.1021/bi990796i] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [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: 11/29/2022]
Abstract
A method is described which allows the selective release and removal of the Bchla-B800 molecules from the LH2 complex of Rhodopseudomonas acidophila 10050. This procedure also allows reconstitution of approximately 80% of the empty binding sites with native Bchla. As shown by circular dichroism spectroscopy, the overall structures of the B850-only and reconstituted complexes are not affected by the pigment-exchange procedure. The pigments reconstituted into the B800 sites can also efficiently transfer excitation energy to the Bchla-B850 molecules.
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Affiliation(s)
- N J Fraser
- Division of Biochemistry and Molecular Biology, IBLS, University of Glasgow, United Kingdom
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10
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Christopoulos G, Perry KJ, Morfis M, Tilakaratne N, Gao Y, Fraser NJ, Main MJ, Foord SM, Sexton PM. Multiple amylin receptors arise from receptor activity-modifying protein interaction with the calcitonin receptor gene product. Mol Pharmacol 1999; 56:235-42. [PMID: 10385705 DOI: 10.1124/mol.56.1.235] [Citation(s) in RCA: 363] [Impact Index Per Article: 14.5] [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: 11/22/2022] Open
Abstract
Receptor activity-modifying proteins (RAMPs) are single-transmembrane proteins that transport the calcitonin receptor-like receptor (CRLR) to the cell surface. RAMP 1-transported CRLR is a calcitonin gene-related peptide (CGRP) receptor. RAMP 2- or RAMP 3-transported CRLR is an adrenomedullin receptor. The role of RAMPs beyond their interaction with CRLR, a class II G protein-coupled receptor, is unclear. In this study, we have examined the role of RAMPs in generating amylin receptor phenotypes from the calcitonin (CT) receptor gene product. Cotransfection of RAMP 1 or RAMP 3 with the human CT receptor lacking the 16-amino acid insert in intracellular domain 1 (hCTRI1-) into COS-7 cells induced specific 125I-labeled rat amylin binding. RAMP 2 or vector cotransfection did not cause significant increases in specific amylin binding. Competition-binding characterization of the RAMP-induced amylin receptors revealed two distinct phenotypes. The RAMP 1-derived amylin receptor demonstrated the highest affinity for salmon CT (IC50, 3.01 +/- 1.44 x 10(-10) M), a high to moderate affinity for rat amylin (IC50, 7.86 +/- 4.49 x 10(-9) M) and human CGRPalpha (IC50, 2.09 +/- 1.63 x 10(-8) M), and a low affinity for human CT (IC50, 4.47 +/- 0.78 x 10(-7) M). In contrast, whereas affinities for amylin and the CTs were similar for the RAMP 3-derived receptor, the efficacy of human CGRPalpha was markedly reduced (IC50, 1.12 +/- 0.45 x 10(-7) M; P <.05 versus RAMP 1). Functional cyclic AMP responses in COS-7 cells cotransfected with individual RAMPs and hCTRI1- were reflective of the phenotypes seen in competition for amylin binding. Confocal microscopic localization of c-myc-tagged RAMP 1 indicated that, when transfected alone, RAMP 1 almost exclusively was located intracellularly. Cotransfection with calcitonin receptor (CTR)I1- induced cell surface expression of RAMP 1. The results of experiments cross-linking 125I-labeled amylin to RAMP 1/hCTR-transfected cells with bis succidimidyl suberate were suggestive of a cell-surface association of RAMP 1 and the receptors. Our data suggest that in the CT family of receptors, and potentially in other class II G protein-coupled receptors, the cellular phenotype is likely to be dynamic in regard to the level and combination of both the receptor and the RAMP proteins.
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Affiliation(s)
- G Christopoulos
- Molecular Pharmacology Laboratory, Department of Pharmacology, The University of Melbourne, Victoria, Australia
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11
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Affiliation(s)
- R J Cogdell
- Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom.
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12
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Fraser NJ, Wise A, Brown J, McLatchie LM, Main MJ, Foord SM. The amino terminus of receptor activity modifying proteins is a critical determinant of glycosylation state and ligand binding of calcitonin receptor-like receptor. Mol Pharmacol 1999; 55:1054-9. [PMID: 10347248 DOI: 10.1124/mol.55.6.1054] [Citation(s) in RCA: 139] [Impact Index Per Article: 5.6] [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: 11/22/2022] Open
Abstract
The calcitonin receptor-like receptor (CRLR) can function as either a receptor for calcitonin gene-related peptide (CGRP) or for adrenomedullin (ADM), depending upon the coexpression of a novel family of single transmembrane proteins, which we have called receptor activity modifying proteins or RAMPs. RAMPs 1, 2, and 3 transport CRLR to the plasma membrane with similar efficiencies, however RAMP1 presents CRLR as a terminally glycosylated, mature glycoprotein and a CGRP receptor, whereas RAMPs 2 and 3 present CRLR as an immature, core glycosylated ADM receptor. Characterization of the RAMP2/CRLR and RAMP3/CRLR receptors in HEK293T cells by radioligand binding (125I-ADM as radioligand), functional assay (cAMP measurement), or biochemical analysis (SDS-polyacrylamide gel electrophoresis) revealed them to be indistinguishable, even though RAMPs 2 and 3 share only 30% identity. Chimeric proteins were created with the transmembrane and cytosolic portions of RAMP1 associated with the amino terminus of RAMP2 (RAMP2/1) and vice versa (RAMP1/2). Coexpression of RAMP2/1 with CRLR formed a core glycosylated ADM receptor, whereas the RAMP1/2 chimera generated both core glycosylated and mature forms of CRLR and enabled both ADM and CGRP receptor binding. Hence, the glycosylation state of CRLR appears to correlate with its pharmacology.
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Affiliation(s)
- N J Fraser
- Receptor Systems, Molecular Pharmacology Unit, GlaxoWellcome Research and Development, Medicines Research Centre, Hertfordshire, United Kingdom
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13
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Gall A, Fraser NJ, Bellissent-Funel MC, Scheer H, Robert B, Cogdell RJ. Bacteriochlorin-protein interactions in native B800-B850, B800 deficient and B800-Bchla(p)-reconstituted complexes from Rhodopseudomonas acidophila, strain 10050. FEBS Lett 1999; 449:269-72. [PMID: 10338146 DOI: 10.1016/s0014-5793(99)00410-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [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: 10/17/2022]
Abstract
Recently, a method which allows the selective release and removal of the 800 nm absorbing bacteriochlorophyll a (B800) molecules from the LH2 complex of Rhodopseudomonas acidophila strain 10050 has been described [Fraser, N.J. (1999) Ph.D. Thesis, University of Glasgow, UK]. This procedure also allows the reconstitution of empty binding sites with the native pigment Bchla(p), esterified with phytol. We have investigated the bacteriochlorophylla-protein interactions in native, B800 deficient (or B850) and in B8110-bacteriochlorophylla(p)-reconstituted LH2 complexes by resonance Raman spectroscopy. We present the first direct structural evidence which shows that the reconstituted pigments are correctly bound within their binding pockets.
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Affiliation(s)
- A Gall
- Section de Biophysique des Protéines et des Membranes, DBCM/CEA and URA2096/CNRS, CEA-Saclay, Gif-sur-Yvette, France
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14
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White JH, Wise A, Main MJ, Green A, Fraser NJ, Disney GH, Barnes AA, Emson P, Foord SM, Marshall FH. Heterodimerization is required for the formation of a functional GABA(B) receptor. Nature 1998; 396:679-82. [PMID: 9872316 DOI: 10.1038/25354] [Citation(s) in RCA: 848] [Impact Index Per Article: 32.6] [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: 12/15/2022]
Abstract
GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the mammalian central nervous system, where it exerts its effects through ionotropic (GABA(A/C)) receptors to produce fast synaptic inhibition and metabotropic (GABA(B)) receptors to produce slow, prolonged inhibitory signals. The gene encoding a GABA(B) receptor (GABA(B)R1) has been cloned; however, when expressed in mammalian cells this receptor is retained as an immature glycoprotein on intracellular membranes and exhibits low affinity for agonists compared with the endogenous receptor on brain membranes. Here we report the cloning of a complementary DNA encoding a new subtype of the GABAB receptor (GABA(B)R2), which we identified by mining expressed-sequence-tag databases. Yeast two-hybrid screening showed that this new GABA(B)R2-receptor subtype forms heterodimers with GABA(B)R1 through an interaction at their intracellular carboxy-terminal tails. Upon expression with GABA(B)R2 in HEK293T cells, GABA(B)R1 is terminally glycosylated and expressed at the cell surface. Co-expression of the two receptors produces a fully functional GABA(B) receptor at the cell surface; this receptor binds GABA with a high affinity equivalent to that of the endogenous brain receptor. These results indicate that, in vivo, functional brain GABA(B) receptors may be heterodimers composed of GABA(B)R1 and GABA(B)R2.
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Affiliation(s)
- J H White
- Receptor Systems, Molecular Pharmacology Unit, GlaxoWellcome, Medicines Research Centre, Stevenage, Hertfordshire, UK
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15
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Abstract
Swiss 3T3 cell lines were constructed co-expressing receptor activity modifying protein (RAMP) 1 with the calcitonin receptor-like receptor (CRLR), and showed 125I-calcitonin-gene-related peptide (CGRP) 1 binding indicative of a type I CGRP receptor. Application of CGRP1 led to an increase in cAMP, which in 2/5 cell lines was augmented following pertussis toxin (PTX) pre-treatment. In Xenopus oocytes, expression of RAMP1, which potentiates an endogenous CGRP receptor, led to constitutive activation of co-expressed GIRK potassium channels. This potassium current was increased following CGRP application or co-expression of CRLR, but decreased by PTX or co-expression of transducin. We conclude that the CGRP receptor can signal to both PTX sensitive and insensitive G proteins.
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Affiliation(s)
- M J Main
- Receptor Systems, Glaxo Wellcome Research Ltd., Medicines Research Centre, Stevenage, Hertfordshire, UK
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McLatchie LM, Fraser NJ, Main MJ, Wise A, Brown J, Thompson N, Solari R, Lee MG, Foord SM. RAMPs regulate the transport and ligand specificity of the calcitonin-receptor-like receptor. Nature 1998; 393:333-9. [PMID: 9620797 DOI: 10.1038/30666] [Citation(s) in RCA: 1570] [Impact Index Per Article: 60.4] [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: 02/07/2023]
Abstract
Calcitonin-gene-related peptide (CGRP) and adrenomedullin are related peptides with distinct pharmacological profiles. Here we show that a receptor with seven transmembrane domains, the calcitonin-receptor-like receptor (CRLR), can function as either a CGRP receptor or an adrenomedullin receptor, depending on which members of a new family of single-transmembrane-domain proteins, which we have called receptor-activity-modifying proteins or RAMPs, are expressed. RAMPs are required to transport CRLR to the plasma membrane. RAMP1 presents the receptor at the cell surface as a mature glycoprotein and a CGRP receptor. RAMP2-transported receptors are core-glycosylated and are adrenomedullin receptors.
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Affiliation(s)
- L M McLatchie
- Receptor Systems and Cell Biology Units, Glaxo Wellcome Medicines Research Centre, Stevenage, Hertfordshire, UK
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17
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Abstract
The EP4 prostaglandin receptor (EP4R) is a member of the seven transmembrane receptor superfamily. We have obtained the human EP4 receptor gene sequence and determined its structure relative to EP4R cDNA synthesized from peripheral blood lymphocytes. The EP4R gene spans approximately 22 kb and consists of three exons separated by two introns. The first exon (530 bp) is noncoding. After an intron of 472 bp, the second exon contains a short (43 bp) 5' sequence before a 289-amino-acid open reading frame (ORF). An 11.5-kb intron is found at the end of transmembrane 6, and the rest of the ORF is in exon 3. The gene structure is analogous to those of the thromboxane, PGI, and PGD receptors. The deduced initiation site does not contain a conventional TATA box but is 70% GC-rich and contains CCAAT boxes, SP1 and AP2 motifs, and motifs consistent with activation by proinflammatory cytokines. Southern blot analysis of human genomic DNA shows two genes with homology to the EP4R gene. Both appear to be pseudogenes with 70% amino acid identity to the EP4R up to the "ERY" sequence at the end of transmembrane 3, where an Alu-like repetitive sequence element was found. The ORF sequence is also interrupted by a stop codon. The pseudogenes differ in that one contains a second "repetitive element" (a line 1 repeat) in the 5' end of the ORF. Northern blot analysis of human mRNA using a pseudogene probe showed hybridization only to the EP4 receptor transcript. PCR also failed to detect expression of either pseudogene. This study defines the gene structure of EP4R and suggests the existence of two related pseudogenes.
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Affiliation(s)
- S M Foord
- Receptor Systems Unit, Glaxo Wellcome Medicines Research Centre, Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2NY, England
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18
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Brown RM, Fraser NJ, Brown GK. Differential methylation of the hypervariable locus DXS255 on active and inactive X chromosomes correlates with the expression of a human X-linked gene. Genomics 1990; 7:215-21. [PMID: 2347586 DOI: 10.1016/0888-7543(90)90543-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.6] [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: 12/31/2022]
Abstract
Consistent differences in methylation of particular cytosine residues in the DNA of active and inactive X chromosomes can be used for rapid, direct analysis of X-inactivation patterns in different female tissues. We have studied methylation of the highly polymorphic DXS255 locus in tissues from patients with deficiency of the E1 alpha subunit of the pyruvate dehydrogenase complex in whom the results can be correlated directly with total enzyme activity, levels of immunoreactive protein, and patterns of cell mosaicism. The results confirm that methylation of the DXS255 locus correlates with X-chromosome expression. In patients and normal controls, the pattern of X inactivation varied widely from tissue to tissue and often deviated markedly from a 50:50 proportion. These deviations are likely to reflect small numbers of tissue-specific stem cells at the time of random X inactivation and cannot be taken alone as evidence for selection or "nonrandom" inactivation.
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Affiliation(s)
- R M Brown
- Murdoch Institute for Research into Birth Defects, Royal Children's Hospital, Melbourne, Australia
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19
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Abstract
Methylation patterns surrounding a hypervariable X-chromosome locus, DXS255, have been analyzed with the restriction enzyme MspI and its methylation-sensitive isoschizomer HpaII. HpaII sites flanking the hypervariable region were found to be methylated on 41 active X chromosomes and unmethylated on 11 inactive X chromosomes present in a range of male, female, and hybrid cells and tissues. This differential methylation pattern coupled with the previously described high level (greater than 90%) of heterozygosity at the DXS255 locus can therefore be applied to determine the inactivation status of X chromosomes in females heterozygous for X-linked disease and in tumor clonality studies.
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Affiliation(s)
- Y Boyd
- Division of Genetics, MRC Radiobiology Unit, Chilton, Didcot, Oxon, England
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20
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Bech-Hansen NT, Field LL, Schramm AM, Reedyk M, Craig IW, Fraser NJ, Pearce WG. A locus for X-linked congenital stationary night blindness is located on the proximal portion of the short arm of the X chromosome. Hum Genet 1990; 84:406-8. [PMID: 1969841 DOI: 10.1007/bf00195809] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [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: 12/29/2022]
Abstract
Linkage between X-linked congenital stationary night blindness (CSNB1) and seven markers on the X chromosome was investigated in a large four-generation Albertan kindred. We detected significant linkage between the CSNB1 locus and the locus DXS255 (maximum lod score = 6.73 at a recombination fraction of 6%; confidence interval of 1% to 18%), which anchors the CSNB1 locus to the proximal region near p11.22 on the short arm of the X chromosome.
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Affiliation(s)
- N T Bech-Hansen
- Alberta Children's Hospital Research Center, Calgary, Canada
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Abrahamson G, Fraser NJ, Boyd J, Craig I, Wainscoat JS. A highly informative X-chromosome probe, M27 beta, can be used for the determination of tumour clonality. Br J Haematol 1990; 74:371-2. [PMID: 2334646 DOI: 10.1111/j.1365-2141.1990.tb02601.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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de Saint Basile G, Arveiler B, Fraser NJ, Boyd Y, Graig IW, Griscelli G, Fischer A. Close linkage of hypervariable marker DXS255 to disease locus of Wiskott-Aldrich syndrome. Lancet 1989; 2:1319-21. [PMID: 2574264 DOI: 10.1016/s0140-6736(89)91920-x] [Citation(s) in RCA: 31] [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] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Linkage analyses in 5 families with Wiskott-Aldrich syndrome show that a novel hypervariable locus, DXS255, is very closely linked to the disease gene on the proximal short arm of the X chromosome. DXS255, with a maximum lod score of 5.42 at theta = 0.00 (90% confidence interval 0.00, 0.10) and heterozygosity of over 90%, is likely to be the closest available marker to the Wiskott-Aldrich gene and to be helpful in genetic counselling of affected families.
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Abstract
A subclone (M27B) has been isolated from a cosmid randomly selected from a library enriched for human X-chromosomal material. The subclone is extensively single-copy sequence, but also contains three complete copies and one partial copy of a 26-bp repeat, within which exists an inverted repeat having the potential to form a cruciform loop structure. Genomic sequences in this repeat region are apparently refractory to cloning, and rearrangements occurring during this process result in deletions. M27B detects multiple X-linked restriction fragments for a wide range of enzymes including MspI and HpaII. We have assigned the locus recognized by the probe (DXS255) to Xcen-Xp11.4 by mapping with a somatic cell hybrid panel and further refined its localization to Xp11.22 by in situ hybridization. The repeat sequence that is presumed to be responsible for the hypervariability observed does not show close similarity to other variable copy number tandem repeats described.
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Affiliation(s)
- N J Fraser
- Genetics Laboratory, University of Oxford, United Kingdom
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Fraser NJ, Boyd Y, Brownlee GG, Craig IW. Multi-allelic RFLP for M27 beta, an anonymous single copy genomic clone at Xp11.3-Xcen [HGM9 provisional no. DXS255]. Nucleic Acids Res 1987; 15:9616. [PMID: 2891116 PMCID: PMC306508 DOI: 10.1093/nar/15.22.9616] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Affiliation(s)
- N J Fraser
- Genetics Laboratory, Department of Biochemistry, Oxford, UK
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