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De Jong-Brink M, Reid CN, Tensen CP, Ter Maat A. Parasites flicking the NPY gene on the host's switchboard: why NPY? FASEB J 1999; 13:1972-84. [PMID: 10544180 DOI: 10.1096/fasebj.13.14.1972] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
It was investigated whether up-regulation of the NPY gene by the schistosome Trichobilharzia ocellata in its snail host Lymnaea stagnalis redirects the host's energy flows. We cloned the cDNA encoding Lymnaea NPY (LyNPY), purified and sequenced the peptide, and used synthesized peptide for physiological and morphological studies. Increasing the LyNPY titer in nonparasitized snails (mimicking parasitosis) by 1) implantation of slow-release pellets and 2) injections suppressed reproductive activity and reduced growth in a dose- and time-dependent manner without affecting food intake. When the LyNPY titer was back to normal, reproduction and growth were resumed, coinciding with a transient increase of food intake serving to replenish glycogen stores. Observations on double-immunostained whole mount preparations of brains support these data. A close association was found between LyNPY-positive axons and axons both from ovulation hormone-producing neurons and molluscan insulin-like peptide-producing neurons involved in regulation of growth. As no synaptic(-like) contacts were observed, it is supposed that LyNPY acts nonsynaptically. No morphological interaction was found between LyNPY-positive axons and motoneurons innervating the feeding apparatus. Our data explain why it is an advantageous strategy for endoparasites to up-regulate the highly conserved NPY gene in their host.
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Affiliation(s)
- M De Jong-Brink
- Department of Developmental Neurobiology, Faculty of Biology, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands.
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52
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Grimmelikhuijzen CJ, Hauser F, Eriksen KK, Williamson M. Invertebrate neurohormones and their receptors. Results Probl Cell Differ 1999; 26:339-62. [PMID: 10453471 DOI: 10.1007/978-3-540-49421-8_15] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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53
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Tensen CP, Flier J, Rampersad SS, Sampat-Sardjoepersad S, Scheper RJ, Boorsma DM, Willemze R. Genomic organization, sequence and transcriptional regulation of the human CXCL 11(1) gene. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1446:167-72. [PMID: 10395932 DOI: 10.1016/s0167-4781(99)00084-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
CXCL 11, encoded by the cDNA sequences designated beta-R1, H-174, or I-TAC, is a CXC chemokine ligand for CXCR3 and assumed to be involved in inflammatory diseases characterized by the presence of activated T-cells. We here describe the genomic organization (four exons interrupted by three introns of 585, 98 and 230 bp) and sequence including 960 bp from the immediate 5'-upstream region of the human CXCL 11 gene. Within the promoter region, consensus sequences for regulatory elements (ISRE, GAS, NF-kappaB) important for cytokine-induced gene transcription were identified. The effect of (pro)inflammatory cytokines on CXCL 11 mRNA expression in monocytic cell lines (THP-1, U937) and primary cultures of dermal fibroblasts and endothelial cells were examined using Northern blot analysis. For these cell types, IFN-gamma was a potent inducer of CXCL 11 transcription, which was synergistically enhanced by TNF-alpha.
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Affiliation(s)
- C P Tensen
- Department of Dermatology, University Hospital Vrije Universiteit, Amsterdam/Leiden Institute for Immunology, 1081 HV, Amsterdam, Netherlands.
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54
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Zendman AJ, Cornelissen IM, Weidle UH, Ruiter DJ, van Muijen GN. TM7XN1, a novel human EGF-TM7-like cDNA, detected with mRNA differential display using human melanoma cell lines with different metastatic potential. FEBS Lett 1999; 446:292-8. [PMID: 10100861 DOI: 10.1016/s0014-5793(99)00230-6] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We have identified a novel 3845 bp cDNA differentially expressed in a human melanoma metastasis model. Northern blot analysis showed expression in the poorly and intermediately metastasizing cell lines and a marked downregulation in the highly metastatic cell lines. Using RT-PCR expression was also seen in several other tumor cell lines and normal cell types of human origin. cDNA sequence analysis revealed an ORF of 687 amino acids containing seven putative transmembrane domains C-terminally and a long N-terminus. The gene was mapped to 16q13. Highest homology was observed with members of the EGF-TM7 subfamily of the secretin/calcitonin receptor family. We propose the delineation of a subfamily of TM7 proteins, LN-TM7, containing seven transmembrane proteins with a long N-terminal extracellular part.
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Affiliation(s)
- A J Zendman
- Department of Pathology, University Hospital, Nijmegen, The Netherlands.
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55
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The lymnaea cardioexcitatory peptide (LyCEP) receptor: a G-protein-coupled receptor for a novel member of the RFamide neuropeptide family. J Neurosci 1998. [PMID: 9822740 DOI: 10.1523/jneurosci.18-23-09812.1998] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A novel G-protein-coupled receptor (GRL106) resembling neuropeptide Y and tachykinin receptors was cloned from the mollusc Lymnaea stagnalis. Application of a peptide extract from the Lymnaea brain to Xenopus oocytes expressing GRL106 activated a calcium-dependent chloride channel. Using this response as a bioassay, we purified the ligand for GRL106, Lymnaea cardioexcitatory peptide (LyCEP), an RFamide-type decapeptide (TPHWRPQGRF-NH2) displaying significant similarity to the Achatina cardioexcitatory peptide (ACEP-1) as well as to the recently identified family of mammalian prolactin-releasing peptides. In the Lymnaea brain, the cells that produce egg-laying hormone are the predominant site of GRL106 gene expression and appear to be innervated by LyCEP-containing fibers. Indeed, LyCEP application transiently hyperpolarizes isolated egg-laying hormone cells. In the Lymnaea pericardium, LyCEP-containing fibers end blindly at the pericardial lumen, and the heart is stimulated by LyCEP in vitro. These data confirm that LyCEP is an RFamide ligand for GRL106.
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56
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Okajima F, Sato K, Tomura H, Kuwabara A, Nochi H, Tamoto K, Kondo Y, Tokumitsu Y, Ui M. Stimulatory and inhibitory actions of lysophosphatidylcholine, depending on its fatty acid residue, on the phospholipase C/Ca2+ system in HL-60 leukaemia cells. Biochem J 1998; 336 ( Pt 2):491-500. [PMID: 9820828 PMCID: PMC1219895 DOI: 10.1042/bj3360491] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We examined the mechanism of action of lysophosphatidylcholine (LPC), which is suggested to be involved in the pathogenesis of atherosclerosis and inflammatory disorders, in HL-60 leukaemia cells. Extracellular 1-palmitoyl LPC increased the intracellular Ca2+ concentration in association with production of inositol phosphate. These actions of LPC were markedly inhibited by treatment of the cells with pertussis toxin and U73122, a phospholipase C inhibitor. The lipid-induced stimulation of the phospholipase C/Ca2+ system was also attenuated in the dibutyryl cAMP-induced differentiated (neutrophil-like) cells, in which phospholipase C activation induced by NaF or formyl-Met-Leu-Phe was enhanced. In contrast with the stimulatory action of 1-palmitoyl LPC, 1-stearoyl LPC was inhibitory for the phospholipase C/Ca2+ system stimulated by NaF as well as by 1-palmitoyl LPC or other Ca2+-mobilizing agonists. In a cell-free system, only an inhibitory effect on phospholipase C activity was observed even by 1-palmitoyl LPC; 1-stearoyl LPC was more inhibitive than 1-palmitoyl LPC. Taken together, these results suggest that atherogenic and inflammatory LPC exerts both stimulatory and inhibitory actions on the phospholipase C/Ca2+ system depending on the species of fatty acid residue of the lipid; the stimulatory effect is possibly mediated through G-protein-coupled receptors; the inhibitory effect might be caused by dysfunction of the components involved in the enzyme system owing to the amphiphilic nature of the lipid. 1-Palmitoyl LPC prefers the former receptor stimulation at least in intact cells, but 1-stearoyl LPC preferentially exerts the latter inhibitory action.
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Affiliation(s)
- F Okajima
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan.
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57
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Tensen CP, Cox KJ, Smit AB, van der Schors RC, Meyerhof W, Richter D, Planta RJ, Hermann PM, van Minnen J, Geraerts WP, Knol JC, Burke JF, Vreugdenhil E, van Heerikhuizen H. The lymnaea cardioexcitatory peptide (LyCEP) receptor: a G-protein-coupled receptor for a novel member of the RFamide neuropeptide family. J Neurosci 1998; 18:9812-21. [PMID: 9822740 PMCID: PMC6793288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
A novel G-protein-coupled receptor (GRL106) resembling neuropeptide Y and tachykinin receptors was cloned from the mollusc Lymnaea stagnalis. Application of a peptide extract from the Lymnaea brain to Xenopus oocytes expressing GRL106 activated a calcium-dependent chloride channel. Using this response as a bioassay, we purified the ligand for GRL106, Lymnaea cardioexcitatory peptide (LyCEP), an RFamide-type decapeptide (TPHWRPQGRF-NH2) displaying significant similarity to the Achatina cardioexcitatory peptide (ACEP-1) as well as to the recently identified family of mammalian prolactin-releasing peptides. In the Lymnaea brain, the cells that produce egg-laying hormone are the predominant site of GRL106 gene expression and appear to be innervated by LyCEP-containing fibers. Indeed, LyCEP application transiently hyperpolarizes isolated egg-laying hormone cells. In the Lymnaea pericardium, LyCEP-containing fibers end blindly at the pericardial lumen, and the heart is stimulated by LyCEP in vitro. These data confirm that LyCEP is an RFamide ligand for GRL106.
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Affiliation(s)
- C P Tensen
- Department of Biochemistry and Molecular Biology, Research Institute Neurosciences, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
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58
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Hsu SY, Liang SG, Hsueh AJ. Characterization of two LGR genes homologous to gonadotropin and thyrotropin receptors with extracellular leucine-rich repeats and a G protein-coupled, seven-transmembrane region. Mol Endocrinol 1998; 12:1830-45. [PMID: 9849958 DOI: 10.1210/mend.12.12.0211] [Citation(s) in RCA: 190] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The receptors for LH, FSH, and TSH belong to the large G protein-coupled, seven-transmembrane (TM) protein family and are unique in having a large N-terminal extracellular (ecto-) domain containing leucine-rich repeats important for interaction with the glycoprotein ligands. We have identified two new leucine-rich repeat-containing, G protein-coupled receptors and named them as LGR4 and LGR5, respectively. The ectodomains of both receptors contain 17 leucine-rich repeats together with N- and C-terminal flanking cysteine-rich sequences, compared with 9 repeats found in known glycoprotein hormone receptors. The leucine-rich repeats in LGR4 and LGR5 are arrays of 24 amino acids showing similarity to repeats found in the acid labile subunit of the insulin-like growth factor (IGF)/IGF binding protein complexes as well as slit, decorin, and Toll proteins. The TM region and the junction between ectodomain and TM 1 are highly conserved in LGR4, LGR5, and seven other LGRs from sea anemone, fly, nematode, mollusk, and mammal, suggesting their common evolutionary origin. In contrast to the restricted tissue expression of gonadotropin and TSH receptors in gonads and thyroid, respectively, LGR4 is expressed in diverse tissues including ovary, testis, adrenal, placenta, thymus, spinal cord, and thyroid, whereas LGR5 is found in muscle, placenta, spinal cord, and brain. Hybridization analysis of genomic DNA indicated that LGR4 and LGR5 genes are conserved in mammals. Comparison of overall amino acid sequences indicated that LGR4 and LGR5 are closely related to each other but diverge, during evolution, from the homologous receptor found in snail and the mammalian glycoprotein hormone receptors. The identification and characterization of new members of the LGR subfamily of receptor genes not only allow future isolation of their ligands and understanding of their physiological roles but also reveal the evolutionary relationship of G protein-coupled receptors with leucine-rich repeats.
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Affiliation(s)
- S Y Hsu
- Department of Gynecology and Obstetrics, Stanford University Medical School, California 94305-5317, USA
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59
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Tensen CP, Cox KJ, Burke JF, Leurs R, van der Schors RC, Geraerts WP, Vreugdenhil E, Heerikhuizen H. Molecular cloning and characterization of an invertebrate homologue of a neuropeptide Y receptor. Eur J Neurosci 1998; 10:3409-16. [PMID: 9824454 DOI: 10.1046/j.1460-9568.1998.00350.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Neuropeptide Y is an abundant and physiologically important peptide in vertebrates having effects on food intake, sexual behaviour, blood pressure and circadian rhythms. Neuropeptide Y homologues have been found in invertebrates, where they are very likely to play similar, important roles. Although five neuropeptide Y-receptor subtypes have been identified in mammals, none has been reported from invertebrates. Here we describe the cloning of a neuropeptide Y-receptor from the brain of the snail Lymnaea stagnalis. The identity of the receptor was deduced by expressing the neuropeptide Y-receptor-encoding cDNA in Chinese Hamster Ovary cells, which were subsequently challenged with size-fractionated Lymnaea brain extracts. An active peptide, selected on the basis of its ability to induce changes in cAMP levels, was purified to homogeneity, analysed by mass spectrometry and amino acid sequence determination, and turned out to be a Lymnaea homologue of neuropeptide Y.
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Affiliation(s)
- C P Tensen
- Department of Biochemistry and Molecular Biology, Graduate School of Neurosciences, Research Institute Neurosciences, Amsterdam, The Netherlands
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60
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Neels J, Horn I, van den Berg B, Pannekoek H, van Zonneveld AJ. Ligand-receptor interactions of the low density lipoprotein receptor-related protein, a multi-ligand endocytic receptor. ACTA ACUST UNITED AC 1998. [DOI: 10.1016/s0268-9499(98)80016-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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61
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Yamazaki H, Bujo H, Saito Y. A novel member of the LDL receptor gene family with eleven binding repeats is structurally related to neural adhesion molecules and a yeast vacuolar protein sorting receptor. J Atheroscler Thromb 1998; 4:20-6. [PMID: 9583350 DOI: 10.5551/jat1994.4.20] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We now have discovered and characterized a novel multi-domain protein and classified it as a member of the LDL receptor gene family. The approximately 250 kDa membrane protein, termed LR11, highly conserved in man, rabbit and chicken, contains a cluster of 11 LDL receptor ligand binding repeats, a group of 5 LDL receptor "YWTD" repeats, a large hexarepeat domain of structural elements found in neural cell adhesion molecules, and a domain with similarity to a yeast receptor for vacuolar protein sorting, VPS10. The cytoplasmic domain exhibits features typical of endocytosis-competent coated pit receptors. The mosaic, and presumably multifunctional, receptor is expressed abundantly in brain, liver and adrenal glands. Ligand blotting of LR11-transfected cells demonstrated that LR11 binds apolipoproteinE-containing lipoproteins, as well as other members of LDL receptor gene family. In contrast to the LDL receptor, the mRNA levels in rabbit liver is unaffected by hyperlipidemia. The features of this highly conserved and complex mosaic protein suggest the importance of the ever expanding LDL receptor gene family in the evolution and proposed multifunctionality.
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Affiliation(s)
- H Yamazaki
- Second Department of Internal Medicine, Chiba University School of Medicine, Japan
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62
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Abstract
The luteinizing hormone receptor (LHR) is a member of the subfamily of glycoprotein hormone receptors within the superfamily of G protein-coupled receptor (GPCR)/seven-transmembrane domain receptors. Over the past eight years, major advances have been made in determining the structure and function of the LHR and its gene. The hormone-binding domain has been localized to exons 1-7 in the extracellular (EC) domain/region of the receptor, which contains several leucine-rich repeats. High-affinity binding of LH and human chorionic gonadotrophin (hCG) causes secondary hormone or receptor contacts to be established with regions of the EC loop/transmembrane module that initiate signal transduction. Models of hormone-receptor interaction have been derived from the crystal structures of hCG and of the ribonuclease inhibitor, which also contains leucine-rich repeats. Such models provide a framework for the interpretation of mutational studies and for further experiments. The extracellular domain of the receptor has been overexpressed in vitro, which will facilitate crystallographic resolution of the structure of the receptor-binding site. The transmembrane domain/loop/cytoplasmic module transduces the signal for coupling to G proteins. Several constitutive, activating mutations that cause human disease have been found in helix VI and adjacent structures. These mutations have provided valuable information about mechanisms of signal transfer and G protein coupling. The structure of the LHR gene has been elucidated, and the regulation of its transcription is beginning to be understood. Valuable insights into receptor evolution have been derived from analysis of sequence homologies, the gene structure of glycoprotein hormone receptors and other members of the GPCR family, and the glycoprotein hormone receptor-like precursors identified in several invertebrate species.
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Affiliation(s)
- M L Dufau
- Molecular Endocrinology Section, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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63
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Sappington TW, Raikhel AS. Ligand-binding domains in vitellogenin receptors and other LDL-receptor family members share a common ancestral ordering of cysteine-rich repeats. J Mol Evol 1998; 46:476-87. [PMID: 9541543 DOI: 10.1007/pl00006328] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Insect vitellogenin and yolk protein receptors (VgR/YPR) are newly discovered members of the low-density lipoprotein receptor (LDLR) family, which is characterized by a highly conserved arrangement of repetitive modular elements homologous to functionally unrelated proteins. The insect VgR/YPRs are unique in having two clusters of complement-type cysteine-rich (class A) repeats or modules, with five modules in the first cluster and seven in the second cluster, unlike classical LDLRs which have a single seven-module cluster, vertebrate VgRs and very low density lipoprotein receptors (VLDLR) which have a single eight-module cluster, and LDLR-related proteins (LRPs) and megalins which have four clusters of 2-7, 8, 10, and 11 modules. Alignment of clusters across subfamilies by conventional alignment programs is problematic because of the repetitive nature of the component modules which may have undergone rearrangements, duplications, and deletions during evolution. To circumvent this problem, we "fingerprinted" each class A module in the different clusters by identifying those amino acids that are both relatively conserved and relatively unique within the cluster. Intercluster reciprocal comparisons of fingerprints and aligned sequences allowed us to distinguish four cohorts of modules reflecting shared recent ancestry. All but two of the 57 modules examined could be assigned to one of these four cohorts designated A, B, C, and D. Alignment of clusters based on modular cohorts revealed that all clusters are derived from a single primordial cluster of at least seven modules with a consensus arrangement of CDCADBC. All extant clusters examined are consistent with this consensus, though none matches it perfectly. This analysis also revealed that the eight-module clusters in vertebrate VgRs, insect VgR/YPRs, and LRP/megalins are not directly homologous with one another. Assignment of modules to cohorts permitted us to properly align 32 class A clusters from all four LDLR subfamilies for phylogenetic analysis. The results revealed that smaller one-cluster and two-cluster members of the family did not originate from the breakup of a large two-cluster or four-cluster receptor. Similarly, the LRP/megalins did not arise from the duplication of a two-cluster insect VgR/YPR-like progenitor. Rather, it appears that the multicluster receptors were independently constructed from the same single-cluster ancestor.
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Affiliation(s)
- T W Sappington
- Department of Entomology, Michigan State University, East Lansing 48824, USA.
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64
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Simoni M, Gromoll J, Nieschlag E. The follicle-stimulating hormone receptor: biochemistry, molecular biology, physiology, and pathophysiology. Endocr Rev 1997; 18:739-73. [PMID: 9408742 DOI: 10.1210/edrv.18.6.0320] [Citation(s) in RCA: 178] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- M Simoni
- Institute of Reproductive Medicine of the University, Münster, Germany
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65
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Helbecque N, Dallongeville J, Codron V, Arveiler D, Ruidavets JB, Evans A, Cambien F, Fruchart JC, Amouyel P. The role of a triplet repeat sequence of the very low density lipoprotein receptor gene in plasma lipid and lipoprotein level variability in humans. Arterioscler Thromb Vasc Biol 1997; 17:2759-64. [PMID: 9409253 DOI: 10.1161/01.atv.17.11.2759] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The biological role of the very low density lipoprotein receptor (VLDL-R) in humans is not yet elucidated. This cellular receptor binds apolipoprotein E (apoE)-containing lipoparticles and is mainly expressed in peripheral tissues. The VLDL-R gene contains a polymorphic triplet (CGG) repeat located 19 bp upstream of the initiation codon. We explored the allelic distribution of this repeat in 1384 subjects of European Caucasian origin, 609 of them surviving a myocardial infarction. Six alleles corresponding to 5, 6, 7, 8, 9, and 11 repeats were detected in this population. The alleles 5, 8, and 9 were the most frequent, with frequencies of 0.413, 0.275, and 0.292, respectively. No association was found between the VLDL-R polymorphism and myocardial infarction. In controls without lipid lowering treatment, a statistically significant interaction between VLDL-R genotype and apoE phenotype was found for plasma triglycerides (P < .04), suggesting a gene-gene interaction. There was also a main effect of the VLDL-R polymorphism on LpE:B and LpA-I. The VLDL-R 9 allele was associated with lower levels of plasma LpE:B (P < .05) and higher concentrations of plasma LpA-I (P < .01) than the other alleles. These results suggest that VLDL-R has a modest influence on circulating lipoproteins in humans.
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Affiliation(s)
- N Helbecque
- Service d'Epidémiologie et de Santé Publique-INSERM CJF 95-05, Institut Pasteur de Lille, France
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66
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Abstract
Apolipoprotein E (apoE) and certain peptides derived from it have been shown to exert neurotoxic effects in vitro, and apoE has been linked to the etiology of Alzheimer's disease. The mechanisms underlying these toxic and pathological effects are, however, not known. To approach this question, we have studied the effects of apoE peptides on the cytoplasmic calcium ([Ca2+]i) homeostasis of cultured cortical neurons. A tandem dimer repeat peptide (apoEdp) derived from the receptor binding domain of apoE was found to have a potent effect on elevation of [Ca2+]i calcium. The pathway by which apoEdp exerted this effect was shown to involve both the mobilization of intracellular calcium and the influx of extracellular calcium, although the effect on influx was more pronounced. Calcium mobilization occurs via a G-protein-linked phospholipase C (PLC) pathway, whereas calcium influx appears to involve a novel Co2+-sensitive channel. Both the mobilization and the influx of calcium require the binding of the apoE peptide to a membrane receptor because both pathways are blocked by antibody to low-density-lipoprotein receptor-related protein. The data suggest that the neurotoxic effects of apoE may be mediated by a persistent elevation of [Ca2+]i.
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Affiliation(s)
- X S Wang
- Neuroscience Graduate Program, University of Cincinnati College of Medicine, Ohio 45267-0524, USA
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67
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Mörwald S, Yamazaki H, Bujo H, Kusunoki J, Kanaki T, Seimiya K, Morisaki N, Nimpf J, Schneider WJ, Saito Y. A novel mosaic protein containing LDL receptor elements is highly conserved in humans and chickens. Arterioscler Thromb Vasc Biol 1997; 17:996-1002. [PMID: 9157966 DOI: 10.1161/01.atv.17.5.996] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Certain receptors belonging to the LDL receptor (LDLR) gene family appear to constitute a newly identified branch whose members are expressed in brain, in addition to other tissues. In support of this concept, we have now discovered the expression and delineated the molecular structures of a representative of this emerging branch from two such diverse species as human and chicken. This membrane receptor, called LR11 and thus far only known to exist in the rabbit, is a complex seven-domain mosaic protein containing, among other structural elements, a cluster of 11 LDLR ligand-binding repeats and a domain with homology to VPS10, a yeast receptor for vacuolar protein sorting. Cytoplasmic signature sequences define the receptor as competent for endocytosis. The most striking properties of LR11s are their (1) high degree of structural conservation (>80% identity among mammals and birds), with 100% identity in the membrane-spanning and cytoplasmic domains of rabbit and human; (2) lack of regulation by cholesterol and estrogen; and (3) expression in brain. The features of LR11 suggest important roles in intercellular and intracellular ligand transport processes, some of which it may share with other brain-specific LDLR family members.
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Affiliation(s)
- S Mörwald
- Department of Molecular Genetics, Biocenter and University of Vienna, Austria
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68
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Cloning, characterization, and expression of a G-protein-coupled receptor from Lymnaea stagnalis and identification of a leucokinin-like peptide, PSFHSWSamide, as its endogenous ligand. J Neurosci 1997. [PMID: 9006965 DOI: 10.1523/jneurosci.17-04-01197.1997] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neuropeptides are known to be important signaling molecules in several neural systems of the pond snail Lymnaea stagnalis. Although the functions of these peptides have been studied in many neurons, the nature of the postsynaptic signal transduction is mainly unknown. The cloning and characterization of neuropeptide receptors in Lymnaea thus would be very valuable in further elucidating peptidergic pathways. Indirect evidence suggests that these neuropeptides operate via G-protein-coupled mechanisms indicating the presence of G-protein-coupled receptors as the initial postsynaptic targets. Here we describe the cloning of a neuropeptide receptor from Lymnaea and the isolation of an endogenous ligand. This peptide, PSFHSWSamide, belongs to the leucokinin family of peptides, and, thus, this Lymnaea receptor is the first example of a leucokinin-like neuropeptide receptor, representing a new subfamily of G-protein-coupled neuropeptide receptors.
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69
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Cox KJ, Tensen CP, Van der Schors RC, Li KW, van Heerikhuizen H, Vreugdenhil E, Geraerts WP, Burke JF. Cloning, characterization, and expression of a G-protein-coupled receptor from Lymnaea stagnalis and identification of a leucokinin-like peptide, PSFHSWSamide, as its endogenous ligand. J Neurosci 1997; 17:1197-205. [PMID: 9006965 PMCID: PMC6793731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/1996] [Revised: 11/07/1996] [Accepted: 11/22/1996] [Indexed: 02/03/2023] Open
Abstract
Neuropeptides are known to be important signaling molecules in several neural systems of the pond snail Lymnaea stagnalis. Although the functions of these peptides have been studied in many neurons, the nature of the postsynaptic signal transduction is mainly unknown. The cloning and characterization of neuropeptide receptors in Lymnaea thus would be very valuable in further elucidating peptidergic pathways. Indirect evidence suggests that these neuropeptides operate via G-protein-coupled mechanisms indicating the presence of G-protein-coupled receptors as the initial postsynaptic targets. Here we describe the cloning of a neuropeptide receptor from Lymnaea and the isolation of an endogenous ligand. This peptide, PSFHSWSamide, belongs to the leucokinin family of peptides, and, thus, this Lymnaea receptor is the first example of a leucokinin-like neuropeptide receptor, representing a new subfamily of G-protein-coupled neuropeptide receptors.
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Affiliation(s)
- K J Cox
- Sussex Centre for Neuroscience, School of Biological Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom
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70
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Gerhardt CC, Bakker RA, Piek GJ, Planta RJ, Vreugdenhil E, Leysen JE, Van Heerikhuizen H. Molecular cloning and pharmacological characterization of a molluscan octopamine receptor. Mol Pharmacol 1997; 51:293-300. [PMID: 9203635 DOI: 10.1124/mol.51.2.293] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
We describe the cloning and functional expression of a cDNA encoding a novel G protein-coupled receptor, which was isolated from the central nervous system of the pond snail Lymnaea stagnalis. The amino acid sequence predicted by this cDNA shows highest similarity with the sequence of the Locusta tyramine receptor, the Drosophila tyramine/octopamine receptor, and the mammalian alpha-adrenergic receptors. On expression in mammalian cells, [3H]rauwolscine, an alpha2-adrenergic receptor antagonist, binds with high affinity (K(D) = 2.9 x 10(-9) M) to the receptor. Of several tested neurotransmitters, octopamine (which is considered to be the invertebrate counterpart of norepinephrine) showed the highest affinity (1.9 x 10(-6) M) for the receptor. Therefore, we consider this receptor to be the first true octopamine receptor to be cloned. The ligand binding properties of the novel receptor, designated Lym oa1, seem to be distinct from any of the binding profiles described for octopamine receptors in tissue preparations. Although the pharmacological profile of Lym oa1 shows some similarity with that of Tyr/Oct-Dro and Tyr-Loc, there are also clear differences. In particular, phentolamine, chlorpromazine, and mianserine display markedly higher affinities for Lym oa1 than for the insect receptors. As far as the vertebrate adrenergic receptors are concerned, the ligand binding properties of Lym oa1 resemble alpha2-adrenergic receptors more than they do alpha- or beta-adrenergic receptors. Octopaminergic stimulation of Lym oa1 induces an increase in both inositol phosphates and cAMP (EC50 = 9.1 x 10(-7) M and 5.1 x 10(-6) M, respectively). This is in contrast to the signal transduction pathways described for the related tyramine- and alpha2-adrenergic receptors, which couple in an inhibitory way to adenylyl cyclase.
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Affiliation(s)
- C C Gerhardt
- Department of Biochemistry and Molecular Biology, Research Institute Neurosciences, Vrije Universiteit, Amsterdam, The Netherlands
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71
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Tensen C, Okuzawa K, Blomenröhr M, Rebers F, Leurs R, Bogerd J, Schulz R, Goos H. Distinct efficacies for two endogenous ligands on a single cognate gonadoliberin receptor. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 243:134-40. [PMID: 9030732 DOI: 10.1111/j.1432-1033.1997.0134a.x] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A cDNA encoding a putative gonadoliberin receptor was cloned from the pituitary of the African catfish. Conceptual translation predicts a protein of 379 amino acids which shows typical characteristics of GTP-binding-protein-coupled receptors. The isolated cDNA was stable expressed in human embryonic kidney (HEK) 293 cells which were used for studies on gonadoliberin-activated second messenger systems (inositol phosphate production; increase in cAMP and/or intracellular Ca2+). The isolated cDNA encoded a functional receptor, designated catfish gonadoliberin receptor (cfGnRH-R), which had an amino acid sequence similarity of 38% with mammalian gonadoliberin receptors. In contrast to its mammalian counterparts which lack an intracellular carboxy-terminal domain, the cfGnRH-R contains an additional 49 amino acid residues. From the two endogenous gonadoliberins in African catfish, chicken gonadoliberin-II had a several hundredfold higher potency than catfish gonadoliberin to activate cfGnRH-R-associated second messenger systems in transfected HEK 293 cells. This is in line with the previously determined higher gonadotropin-release capacity of chicken gonadoliberin-II in catfish. Stimulation of second messenger systems with chicken gonadoliberin-II, but not with catfish gonadoliberin, resulted in a biphasic effect and chicken gonadoliberin-II led to a higher maximum stimulation than catfish gonadoliberin. Challenging cfGnRH-R simultaneously with chicken gonadoliberin-II and catfish gonadoliberin did not lead to additive effects. In contrast, two types of mutual inhibitory effects were recorded. These data indicate that a single cognate cfGnRH-R couples with distinct efficacies to signal transduction systems upon stimulation by the two endogenous gonadoliberins which, in addition, may interact negatively.
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Affiliation(s)
- C Tensen
- Department of Experimental Zoology, University of Utrecht, The Netherlands
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72
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Hauser F, Nothacker HP, Grimmelikhuijzen CJ. Molecular cloning, genomic organization, and developmental regulation of a novel receptor from Drosophila melanogaster structurally related to members of the thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone/choriogonadotropin receptor family from mammals. J Biol Chem 1997; 272:1002-10. [PMID: 8995395 DOI: 10.1074/jbc.272.2.1002] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Using oligonucleotide probes derived from consensus sequences for glycoprotein hormone receptors, we have cloned an 831-amino acid residue-long receptor from Drosophila melanogaster that shows a striking structural homology with members of the glycoprotein hormone (thyroid-stimulating hormone (TSH); follicle-stimulating hormone (FSH); luteinizing hormone/choriogonadotropin (LH/CG)) receptor family from mammals. This homology includes a very large, extracellular N terminus (20% sequence identity with rat TSH, 19% with rat FSH, and 20% with the rat LH/CG receptor) and a seven-transmembrane region (53% sequence identity with rat TSH, 50% with rat FSH, and 52% with the rat LH/CG receptor). The Drosophila receptor gene is >7.5 kilobase pairs long and contains 17 exons and 16 introns. Seven intron positions coincide with introns in the mammalian glycoprotein hormone receptor genes and have the same intron phasing. This indicates that the Drosophila receptor is evolutionarily related to the mammalian receptors. The Drosophila receptor gene is located at position 90C on the right arm of the third chromosome. The receptor is strongly expressed starting 8-16 h after oviposition, and the expression stays high until after pupation. Adult male flies express high levels of receptor mRNA, but female flies express about 6 times less. The expression pattern in embryos and larvae suggests that the receptor is involved in insect development. This is the first report on the molecular cloning of a glycoprotein hormone receptor family member from insects.
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Affiliation(s)
- F Hauser
- Department of Cell Biology and Anatomy, Zoological Institute, University of Copenhagen, Denmark
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73
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Ziere GJ, van der Kaaden ME, Vogelezang CJ, Boers W, Bihain BE, Kuiper J, Kruijt JK, van Berkel TJ. Blockade of the alpha 2-macroglobulin receptor/low-density-lipoprotein-receptor-related protein on rat liver parenchymal cells by the 39-kDa receptor-associated protein leaves the interaction of beta-migrating very-low-density lipoprotein with the lipoprotein remnant receptor unaffected. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 242:703-11. [PMID: 9022700 DOI: 10.1111/j.1432-1033.1996.0703r.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The nature of the liver binding site which is responsible for the initial recognition and clearance of chylomicron-remnants and beta-migrating very-low-density lipoprotein (beta-VLDL) is under active dispute. We have investigated the effect of the 39-kDa receptor-associated protein (RAP) on the recognition site for activated alpha 2-macroglobulin and beta-VLDL on rat liver parenchymal cells in vivo and in vitro in order to analyze whether both substrates are recognized and internalized by the same receptor system. Radiolabelled trypsin-activated alpha 2-macroglobulin (alpha 2M-T) was cleared rapidly by the liver (maximal uptake of 80.8 +/- 1.0% of the injected dose). Prior injection of 5, 15, or 50 mg gluthathione-S-transferase-linked RAP (GST-RAP)/kg rat reduced the liver uptake to 62.2 +/- 2.3%, 59.3 +/- 1.1%, or 2.9 +/- 0.1% of the injected dose, respectively. Concurrently the serum decay was strongly delayed after injection of 50 mg GST-RAP/kg rat but this did not affect the serum decay and liver uptake of 125I-beta-VLDL. Binding studies with isolated liver parenchymal cells in vitro demonstrated that the binding of 125I-alpha 2M-T was 98% inhibited by GST-RAP with an IC50 of 0.3 microgram/ml (4.2 nM), whereas the binding of 125I-beta-VLDL and 125I-beta-VLDL + recombinant apolipoprotein E (rec-apoE) was unaffected by GST-RAP up to 50 micrograms/ml (700 nM). Also, the cell association and degradation of alpha 2M-T was blocked by RAP, while the association and degradation of beta-VLDL and beta-VLDL + rec-apoE were not influenced. The inhibitory effect of RAP on the cell association and degradation of alpha 2M-T lasted for 1-2 h of incubation at 37 degrees C. The binding of the radioiodinated RAP to isolated liver parenchymal cells was highly efficiently coupled to lysosomal degradation. Upon in vivo injection into rats, 125I-labeled RAP is rapidly cleared from the serum and taken up by the liver, which is also coupled to efficient degradation. Since RAP blocks binding of all known ligands to the alpha 2-macroglobulin receptor/low-density lipoprotein receptor-related protein (the alpha 2Mr/LRP) and at high concentrations the binding to the LDL receptor, we conclude that the initial binding and internalization of beta-VLDL by rat liver parenchymal cells is not mediated by the alpha 2Mr/LRP. The properties of binding of beta-VLDL to rat liver parenchymal cells points to an apoE-specific recognition site for lipoprotein remnants which differs from the alpha 2Mr/LRP, proteoglycans and the LDL receptor and is tentatively called the lipoprotein remnant receptor.
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Affiliation(s)
- G J Ziere
- Division of Biopharmaceutics, Leiden/Amsterdam Center for Drug Research, University of Leiden, The Netherlands
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74
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Kosugi S, Mori T, Shenker A. The role of Asp578 in maintaining the inactive conformation of the human lutropin/choriogonadotropin receptor. J Biol Chem 1996; 271:31813-7. [PMID: 8943222 DOI: 10.1074/jbc.271.50.31813] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
A constitutively activating mutation encoding Asp578-->Gly in transmembrane helix 6 of the lutropin/choriogonadotropin receptor (LHR) is the most common cause of gonadotropin-independent, male-limited precocious puberty. This mutant LHR produces a 4.5-fold increase in basal cAMP when expressed in COS-7 cells. To better understand the normal role of Asp578 in the LHR we studied the effect of seven other amino acid substitutions at this position. No agonist binding or response was detected with the Asp578-->Pro mutant. Agonist binding affinity was unaffected by the other substitutions and estimated receptor concentrations ranged from 11 to 184% of wild type. Substitution of Asp578 with Asn, a similarly sized, uncharged residue, did not produce agonist-independent activation. In contrast, replacement with Glu, Ser, or Leu caused 4. 9-5.6-fold stimulation of basal cAMP. Substitution with Tyr (8.5-fold) or Phe (7.5-fold) had a greater activating effect. Only the Tyr, Phe, and Leu mutants showed constitutive activation of the inositol phosphate pathway. Our data suggest that it is the ability of the Asp578 side chain to serve as a properly positioned hydrogen bond acceptor, rather than its negative charge, that is important for stabilizing the inactive state of the LHR. A bulky aromatic side chain at position 578 may further destabilize the inactive receptor conformation.
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Affiliation(s)
- S Kosugi
- Department of Laboratory Medicine, Kyoto University School of Medicine, Kyoto 606-01, Japan.
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75
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Jacobsen L, Madsen P, Moestrup SK, Lund AH, Tommerup N, Nykjaer A, Sottrup-Jensen L, Gliemann J, Petersen CM. Molecular characterization of a novel human hybrid-type receptor that binds the alpha2-macroglobulin receptor-associated protein. J Biol Chem 1996; 271:31379-83. [PMID: 8940146 DOI: 10.1074/jbc.271.49.31379] [Citation(s) in RCA: 196] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The 39-40-kDa receptor-associated protein (RAP) binds to the members of the low density lipoprotein receptor gene family and functions as a specialized endoplasmic reticulum/Golgi chaperone. Using RAP affinity chromatography, we have purified a novel approximately 250-kDa brain protein and isolated the corresponding cDNA. The gene, designated SORL1, maps to chromosome 11q 23/24 and encodes a 2214-residue type 1 receptor containing a furin cleavage site immediately preceding the N terminus determined in the purified protein. The receptor, designated sorLA-1, has a short cytoplasmic tail containing a tyrosine-based internalization signal and a large external part containing (from the N-terminal): 1) a segment homologous to domains in the yeast vacuolar protein sorting 10 protein, Vps10p, that binds carboxypeptidase Y, 2) five tandemly arranged YWTD repeats and a cluster of 11 class A repeats characteristic of the low density lipoprotein receptor gene family receptors, and 3) six tandemly arranged fibronectin type III repeats also found in certain neural adhesion proteins. sorLA-1 may therefore be classified as a hybrid receptor. Northern blotting revealed specific mRNA transcripts in brain, spinal cord, and testis but not in several major organs. Both RAP and an antibody against a synthetic peptide derived from a sequence determined in the mature protein detected sorLA-1 in crude human brain extracts. The domain structure suggests that sorLA-1 is an endocytic receptor possibly implicated in the uptake of lipoproteins and of proteases.
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Affiliation(s)
- L Jacobsen
- Department of Medical Biochemistry, University of Aarhus, DK-8000 Aarhus C, Denmark
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76
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Yamazaki H, Bujo H, Kusunoki J, Seimiya K, Kanaki T, Morisaki N, Schneider WJ, Saito Y. Elements of neural adhesion molecules and a yeast vacuolar protein sorting receptor are present in a novel mammalian low density lipoprotein receptor family member. J Biol Chem 1996; 271:24761-8. [PMID: 8798746 DOI: 10.1074/jbc.271.40.24761] [Citation(s) in RCA: 152] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Normal cell development depends to a large part on multifunctional proteins that have evolved by recombination of proven modular elements. We now have discovered and characterized in rabbit such a multi-domain protein, and classify it as novel member of the low density lipoprotein (LDL) receptor gene family. The extracellular portion of the approximately 250-kDa membrane protein, termed LR11, contains a cluster of 11 LDL receptor ligand binding repeats, a group of 5 LDL receptor "YWTD" repeats, a large hexarepeat domain of structural elements found in neural cell adhesion molecules, and a domain with similarity to a yeast receptor for vacuolar protein sorting, VPS10. The cytoplasmic domain exhibits features typical of endocytosis-competent coated-pit receptors. The mosaic, and presumably multifunctional, receptor is expressed abundantly in brain, in particular the hippocampus, dentate gyrus, and cerebral cortex, and is present at significant levels in liver, adrenal glands, and testis. Western blotting of tissues and ligand blotting of LR11-transfected cells demonstrated that the novel protein binds apolipoprotein E-containing lipoproteins. In contrast to the LDL receptor, hepatic expression of LR11 is unaffected by hyperlipidemia. The identification of this highly conserved and superbly complex protein offers the opportunity to gain new insights into the emergence of multifunctional mosaic proteins akin to the ever expanding LDL receptor gene family.
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Affiliation(s)
- H Yamazaki
- Second Department of Internal Medicine, Chiba University School of Medicine, Chiba 260, Japan
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77
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Bochkov VN, Tkachuk VA, Philippova MP, Stambolsky DV, Bühler FR, Resink TJ. Ligand selectivity of 105 kDa and 130 kDa lipoprotein-binding proteins in vascular-smooth-muscle-cell membranes is unique. Biochem J 1996; 317 ( Pt 1):297-304. [PMID: 8694779 PMCID: PMC1217478 DOI: 10.1042/bj3170297] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Using ligand blotting techniques, with low-density lipoprotein (LDL) as ligand, we have previously described the existence of atypical lipoprotein-binding proteins (105 kDa and 130 kDa) in membranes from human aortic medical tissue. The present study demonstrates that these proteins are also present in membranes from cultured human (aortic and mesenteric) and rat (aortic) vascular smooth-muscle cells (VSMCs). To assess the relationship of 105 and 130 kDa lipoprotein-binding proteins to known lipoprotein receptors, ligand binding specificity was studied. We tested effects of substances known to antagonize ligand binding to either the LDL [apolipoprotein B,E (apo B,E)] receptor (dextran sulphate, heparin, pentosan polysulphate, protamine, spermine, histone), the scavenger receptor (dextran sulphate, fucoidin), the very-low-density-lipoprotein (VLDL) receptor [receptor-associated protein (RAP)], or LDL receptor-related protein (RAP, alpha 2-macroglobulin, lipoprotein lipase, exotoxin-A). None of these substances, with the exception of dextran sulphate, influenced binding of LDL to either 105 or 130 kDa proteins. Sodium oleate or oleic acid, known stimuli for the lipoprotein binding activity of the lipolysis-stimulated receptor, were also without effect. LDL binding to 105 and 130 kDa proteins was inhibited by anti-LDL (apo B) antibodies. LDL and VLDL bound to 105 and 130 kDa proteins with similar affinities (approximately 50 micrograms/ml). The unique ligand selectivity of 105 and 130 kDa proteins supports the existence of a novel lipoprotein-binding protein that is distinct from all other currently identified LDL receptor family members. The similar ligand selectivity of 105 and 130 kDa proteins suggests that they may represent variant forms of an atypical lipoprotein-binding protein.
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Affiliation(s)
- V N Bochkov
- Laboratory of Molecular Endocrinology, Cardiology Research Center, Moscow, Russia
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78
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Mehta KD, Chang R, Norman J. Chiloscyllium plagiosum low-density lipoprotein receptor: evolutionary conservation of five different functional domains. J Mol Evol 1996; 42:264-72. [PMID: 8919878 DOI: 10.1007/bf02198853] [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: 02/03/2023]
Abstract
All five functional domains of the low-density lipoprotein (LDL) receptor were assembled in their modern form more than 450 million years ago, as revealed from the cloning and sequencing of an LDL receptor cDNA from Chiloscyllium plagiosum (banded cat shark). The shark LDL receptor has the same overall architecture as the mammalian and amphibian counterparts. Each of the seven cysteine-rich repeats in the ligand binding domain resembles its counterpart in the human LDL receptor more than it does the other repeats in the shark receptor as suggested by the presence of unique "signature" sequences, indicating that these repeats had already acquired their independent structures by the time of shark development. Furthermore, amino acid sequences of the entire ligand binding domain of shark LDL receptor show 35% identity over a stretch of 294 residues with a Lymnaea stagnalis G-protein-linked receptor (LSGLR). The region of homology between these unrelated proteins includes conservation of most of the unique characteristics of the cysteine-rich repeats of LDL receptor at the expected positions in LSGLR. The results presented are consistent with the hypothesis that all seven repeats in the ligand binding domain of LDL receptor may have been lifted directly from an ancestral gene instead of being evolutionary duplications of a single repeat recruited by the primitive LDL receptor from another gene.
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Affiliation(s)
- K D Mehta
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock 72205, USA
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79
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Grimmelikhuijzen CJ, Leviev I, Carstensen K. Peptides in the nervous systems of cnidarians: structure, function, and biosynthesis. INTERNATIONAL REVIEW OF CYTOLOGY 1996; 167:37-89. [PMID: 8768492 DOI: 10.1016/s0074-7696(08)61345-5] [Citation(s) in RCA: 123] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Cnidarians are the lowest animal group having a nervous system and it was probably within this phylum or in a related ancestor group that nervous systems first evolved. The primitive nervous systems of cnidarians are strongly peptidergic. From a single sea anemone species, Anthopleura elegantissima, 17 different neuropeptides have been isolated so far, and we expect that many more neuropeptides (more than 30) must be present. All peptides are localized in neurons of cnidarians and we have demonstrated the presence of some of the peptides in neurosecretory dense-cored vesicles. Most neuropeptides have an excitatory or inhibitory action on whole cnidarians, muscle preparations, and isolated muscle cells, suggesting that these peptides are neurotransmitters or neuromodulators. One neuropeptide induces metamorphosis in planula larvae to become a polyp. This shows that cnidarian neuropeptides also are involved in developmental processes, such as cell differentiation and pattern formation. We have cloned the preprohormones for most of the cnidarian neuropeptides. These preprohormones have a high copy number of the immature neuropeptide sequence, which can be up to 37 neuropeptide copies per precursor molecule. In addition to well-known, "classical" processing enzymes, novel prohormone processing enzymes must be present in cnidarian neurons. These include a processing enzyme hydrolyzing at the C-terminal sides of acidic (Asp and Glu) residues and a dipeptidyl aminopeptidase digesting at the C-terminal sides of N-terminally located X-Pro and X-Ala sequences. All this shows that the primitive nervous systems of cnidarians are already quite complex, and that neuropeptides play a central role in the physiology of these animals.
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80
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Guevara J, Walch ET, Epstein HF, Sparrow JT, Gotto AM, Valentinova NV. Evidence that apoB-100 of low-density lipoproteins is a novel Src-related protein kinase. JOURNAL OF PROTEIN CHEMISTRY 1995; 14:627-31. [PMID: 8561859 DOI: 10.1007/bf01886889] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Protein-tyrosine kinases of signal transduction pathways occur and function intracellularly. In contrast, the low-density lipoprotein (LDL) particle circulates in plasma, where its function is to solubilize and transport lipid. Recently, several reports showed that LDL may have a role in signal transduction. We have identified a region in the apoB-100 primary structure which shows similarity to Src-homology-1 (SH1) domains, the kinase region of protein-tyrosine kinases. Results obtained in protein kinase assays of highly purified LDL showed that only the apoB-100 was phosphorylated, suggesting that apoB-100 has the capacity to undergo autophosphorylation like known protein-tyrosine kinases. Phosphorylation was not observed for any other apolipoprotein in LDL or for any component of high-density lipoprotein and lipoprotein [a]. Our results suggest that apoB-100 may be a novel and functional member of the src protein kinase family.
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Affiliation(s)
- J Guevara
- Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA
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81
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Abstract
Leucine-rich repeats are short sequence motifs present in over sixty proteins, all of which appear to be involved in protein-protein interactions. The crystal structure of ribonuclease inhibitor demonstrated that the repeats correspond to beta-alpha structural units. The recently determined crystal structure of the ribonuclease A-ribonuclease inhibitor complex suggests the basis for the protein-binding function of leucine-rich repeats.
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Affiliation(s)
- B Kobe
- St Vincent's Institute of Medical Research, Fitzroy, Australia
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82
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Knol JC, Ramnatsingh S, Kesteren ER, Minnen J, Planta RJ, Heerikhuizen H, Vreugdenhil E. Cloning of a Molluscan G Protein alpha Subunit of the Gq Class which is Expressed Differentially in Identified Neurons. ACTA ACUST UNITED AC 1995. [DOI: 10.1111/j.1432-1033.1995.tb20550.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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83
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Schackelford RE, Misra UK, Florine-Casteel K, Thai SF, Pizzo SV, Adams DO. Oxidized low density lipoprotein suppresses activation of NF kappa B in macrophages via a pertussis toxin-sensitive signaling mechanism. J Biol Chem 1995; 270:3475-8. [PMID: 7876078 DOI: 10.1074/jbc.270.8.3475] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The interaction of oxidized low density lipoprotein (ox-LDL) and macrophages is generally believed to be a significant inductive step in atherogenesis. Endocytosis of ox-LDL by scavenger receptors (SR) on macrophages is one result of this interaction, as is suppressed expression of several lipopolysaccharide (LPS)-stimulated, inflammatory genes such as tumor necrosis factor-alpha (TNF-alpha). Events subsequent to SR ligation, including intracellular signaling events if any, have not been established. We report here that ox-LDL initiates rapid hydrolysis of phosphatidylinositol 4,5-bisphosphate 2 (PIP2) and intracellular fluxes of Ca2+ in macrophages, both of which are sensitive to pertussis toxin. ox-LDL also suppresses the LPS-induced binding of macrophage extracts to an NF kappa B sequence oligonucleotide and the LPS-initiated accumulation of RNA specific for TNF-alpha. These latter two effects are pertussis toxin-sensitive. Ligation of SR by ox-LDL thus initiates a pertussis toxin-sensitive signaling pathway in macrophages, which involves hydrolysis of PIP2 and which can suppress expression of the TNF-alpha gene by modulating activation of NF kappa B.
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Affiliation(s)
- R E Schackelford
- Department of Pathology, Duke University Medical Center, Durham, North Carolina 27710
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84
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Kosugi S, Shenker A, Mori T. Constitutive activation of cyclic AMP but not phosphatidylinositol signaling caused by four mutations in the 6th transmembrane helix of the human thyrotropin receptor. FEBS Lett 1994; 356:291-4. [PMID: 7805857 DOI: 10.1016/0014-5793(94)01286-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Four different somatic mutations (F631C, T632I, D633E, and D633Y) in the putative 6th transmembrane helix of the human thyrotropin receptor (TSHR) were recently described in hyperfunctioning thyroid adenomas [Porcellini et al. (1994) J. Clin. Endocrinol. Metab. 79, 657-661]. We transiently expressed these mutant receptors in Cos-7 cells and measured [125I]TSH binding, basal and TSH-stimulated cAMP production, and phosphatidylinositol hydrolysis. The concentration of receptors expressed at the cell surface was lower for the mutants than for the wild type (WT) TSHR. Compared to the WT, all four mutant receptors caused a marked increase in basal cAMP levels, but did not increase basal production of inositol phosphates. This suggests that autonomous thyroid function and adenoma formation may be related to constitutive activation of the cAMP pathway alone. A cluster of conserved residues at the base of the 6th transmembrane helix of the TSHR and other glycoprotein hormone receptors appears important for maintaining an inactive receptor conformation.
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Affiliation(s)
- S Kosugi
- Department of Laboratory Medicine, Kyoto University School of Medicine, Japan
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