Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The GnRH receptor (GnRH-R) is a cell surface, G protein-coupled receptor that is highly expressed in pituitary gonadotropes. Activation of the receptor by GnRH stimulates the release of FSH and LH. Pituitary GnRH-R numbers and, hence, gonadotrope responsiveness to GnRH vary under different conditions and are regulated to a large extent by GnRH itself. To study the transcriptional regulation of the GnRH-R gene, a genomic clone containing 1.2 kilobases (kb) of the 5'-flanking region of mouse GnRH-R gene was isolated and characterized. A major transcriptional start site was identified 62 nucleotides upstream of the translational start site by primer extension and ribonuclease protection analyses. The promoter region does not contain canonical TATA sequences in the appropriate location. To determine whether this putative promoter is functional, it was subcloned into a luciferase reporter plasmid (GnRH-RLuc), and its transient expression was studied in cell lines of gonadotrope (alpha T3-1) and somatolactotrope (GH3) origins as well as those of nonpituitary origin (JEG-3 and CV-1). Luciferase activity was increased in alpha T3-1 (246-fold +/- 34.5-fold; P < 0.005) compared with the promoterless vector control but was considerably lower in GH3 (41-fold +/- 3.9-fold; P < 0.005), JEG-3 (12-fold +/- 0.9-fold; P < 0.005) and CV-1 (8-fold +/- 1.3-fold) indicating that GnRH-RLuc is preferentially expressed in cells of gonadotrope origin. Furthermore, GnRH agonist stimulated luciferase activity 3.4-fold +/- 0.3-fold (P < 0.005) above basal levels in GH3 cells cotransfected with rat GnRH-R complementary DNA, indicating that the GnRH-R promoter sequence is responsive to this ligand. In summary, we have identified and partially characterized the promoter region of the mouse GnRH-R and demonstrated that the regulatory elements for tissue-specific expression as well as for GnRH regulation are present within a 1.2-kb 5'-flanking region of the mouse GnRH-R gene.
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PMID:Isolation and characterization of the 5'-flanking region of the mouse gonadotropin-releasing hormone receptor gene. 798 11

The principal mechanism of homologous desensitization of the beta-adrenergic receptor (beta2AR) is phosphorylation of the receptor by the betaAR kinase (betaARK) or other closely related G protein-coupled receptor kinases (GRKs). However, within a single organ such as the lung where many cell types express the receptor, the presence or extent of beta2AR desensitization in different cells has been noted to be highly variable. We hypothesized that such variability in desensitization is due to significant cell-type differences in betaARK expression and/or function. To approach this, in situ hybridization was carried out in the lung and indeed revealed heterogeneity in betaARK gene expression. Quantitative studies using ribonuclease protection assays with cell lines revealed that the level of betaARK mRNA in airway smooth muscle cells was approximately 20% of that in bronchial epithelial cells and approximately 11% of that in mast cells (6.65 +/- 0.96 versus 32.6 +/- 4.0 and 60.7 +/- 1.5 relative units, respectively, p < 0. 001). betaARK2 gene expression was not detected in any of these cells. At the protein level, betaARK expression in airway smooth muscle cells was nearly undetectable, being approximately 10-fold less than that expressed on mast cells. The activities of the GRKs in cell extracts were assessed in vitro by quantitating their ability to phosphorylate rhodopsin in the presence of light. Consistent with the gene and protein expression results, a marked discrepancy in activities was observed between extracts derived from mast cells (90.7 +/- 0.5 relative units) as compared to airway smooth muscle cells (9.28 +/- 0.6 relative units, p < 0.001). In contrast, the activities of protein kinase A (the other kinase that phosphorylates beta2AR) in these extracts were not different. We predicted, then, that airway smooth muscle beta2AR would undergo minimal short-term (5 min) agonist-promoted desensitization as compared to the beta2AR expressed on mast cells. Mast cell cAMP reached maximal levels after 90 s and did not further increase over time, indicative of receptor desensitization in this cell. In contrast, cAMP levels of airway smooth muscle cells did not plateau, increasing at a rate of 103 +/- 9% per min, consistent with little desensitization over the study period. We conclude that there is significant cell-type variation in expression of betaARK and that such variation is directly related to the extent of short-term agonist-promoted desensitization of the beta2AR.
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PMID:Heterogeneity in beta-adrenergic receptor kinase expression in the lung accounts for cell-specific desensitization of the beta2-adrenergic receptor. 905 32

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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PMID:The luteinizing hormone receptor. 955 73

Protease-activated receptors (PARs) are members of the G protein-coupled receptor superfamily that are activated by the proteolytic cleavage of their amino terminal domain. PAR-1 activation by thrombin results in several biologic effects, including platelet adhesion to other cells or extracellular matrix, fibroblast, and endothelial cell growth, whereas PAR-2, activated by trypsin, has mainly a proinflammmatory and angiogenetic role. PAR-1 and PAR-2 modulate cell proliferation in physiopathologic cell invasion processes, suggesting that they may play a role in the setting of cancer growth and metastasis. Here, we have investigated the expression of PAR-1 and PAR-2 proteins by immunohistochemistry in a series of benign and malignant melanocytic lesions: 20 melanocytic lesions (10 common melanocytic nevi and 10 atypical or "dysplastic" melanocytic nevi) and 50 melanomas (10 in situ melanomas, 10 melanomas T1, 10 melanomas T2, 10 melanomas T3 to T4, and 10 metastatic melanomas). PAR-1 was significantly overexpressed in atypical nevi and melanomas in comparison with common melanocytic nevi. PAR-2 was strongly and diffusely expressed by immunohistochemistry in all melanocytic lesions, with no statistically significant differences between nevi and melanomas. Because we found a differential expression in PAR-1 protein, but not in PAR-2, we next investigated the expression of PAR-1 messenger RNA (mRNA) by ribonuclease protection assay in paraffin-embedded tissues using a paraffin block RNA isolation procedure. Similarly to immunohistochemical results, PAR-1 mRNA expression was significantly higher in atypical nevi and melanomas in comparison with common nevi and controls. Overexpression of PAR-1 in atypical nevi and melanomas supports a role for PAR-1 in the initial phases of melanoma development as well as in tumor progression and metastasis. Conversely, the significance of PAR-2 up-regulation in both benign and malignant melanocytic lesions requires further research.
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PMID:Expression of protease-activated receptors 1 and 2 in melanocytic nevi and malignant melanoma. 1602 75

Recently, we isolated a subset of glycolipoproteins from Panax ginseng, that we designated gintonin, and demonstrated that it induced [Ca2+]i transients in cells via G protein-coupled receptor (GPCR) signaling pathway(s). However, active components responsible for Ca2+ mobilization and the corresponding receptor(s) were unknown. Active component(s) for [Ca2+]i transients of gintonin were analyzed by liquid chromatography-electrospray ionization-tandem mass spectrometry and ion-mobility mass spectrometry, respectively. The corresponding receptor(s)were investigated through gene expression assays. We found that gintonin contains LPA C18:2 and other LPAs. Proteomic analysis showed that ginseng major latex-like protein and ribonuclease-like storage proteins are protein components of gintonin. Gintonin induced [Ca2+]i transients in B103 rat neuroblastoma cells transfected with human LPA receptors with high affinity in order of LPA2 >LPA5 > LPA1 > LPA3 > LPA4. The LPA1/LPA3 receptor antagonist Ki16425 blocked gintonin action in cells expressing LPA1 or LPA3. Mutations of binding sites in the LPA3 receptor attenuated gintonin action. Gintonin acted via pertussis toxin (PTX)-sensitive and -insensitive G protein-phospholipase C (PLC)-inositol 1,4,5-trisphosphate (IP3)-Ca2+ pathways. However, gintonin had no effects on other receptors examined. In human umbilical vein endothelial cells (HUVECs) gintonin stimulated cell proliferation and migration. Gintonin stimulated ERK1/2 phosphorylation. PTX blocked gintonin-mediated migration and ERK1/2 phosphorylation. In PC12 cells gintonin induced morphological changes, which were blocked by Rho kinase inhibitorY-27632. Gintonin contains GPCR ligand LPAs in complexes with ginseng proteins and could be useful in the development of drugs targeting LPA receptors.
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PMID:Gintonin, newly identified compounds from ginseng, is novel lysophosphatidic acids-protein complexes and activates G protein-coupled lysophosphatidic acid receptors with high affinity. 2228 31