Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Binding sites for prolactin were identified in a plasma-membrane-enriched fraction isolated from livers of mature female rats. 125I-labelled sheep prolactin prepared by the lactoperoxidase procedure retained the same molecular integrity and binding affinity as the native hormone at physiological pH. The receptors bound prolactin from different species, whereas non-lactogenic hormones were not bound. The binding of 125I-labelled sheep prolactin was activated equally by bivalent and univalent cations, bivalent cations exerting their maximal effect at much lower concentrations. The association of 125I-labelled sheep prolactin with the receptor was a time- and temperature-dependent process. Partial dissociation was detected. The binding of 125I-labelled sheep prolactin was strongly influenced by pH, with an optimum observed at pH 6.5. Receptor activity was destroyed by Pronase and phospholipase C, whereas neuraminidase increased binding. Treatment of the membranes by ribonuclease and deoxyribonuclease did not affect the binding. Binding of 125I-labelled sheep prolactin was inhibited by p-chloromercuribenzoic acid, dithiothreitol and by brief exposure to high temperatures. Scatchard analysis of the binding of 125I-labelled sheep prolactin to receptors indicated that prolactin has a high affinity for its receptor. Binding of prolactin to liver membranes showed some properties different from those observed with mammary cells. Binding by these tissues differed in pH optimum, in effects of ions, and in response to neuraminidase.
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PMID:Characterization of prolactin binding by membrane preparations from rat liver. 3 84

Previous studies have shown that a membrane preparation from hen oviduct catalyzes transfer of oligosaccharide from oligosaccharide-P-P-dolichol to denatured RNase and alpha-lactalbumin. To gain further insight into the structural requirements of a protein that allow it to serve as a substrate for glycosylation, the acceptor ability of a variety of other modified proteins containing the tripeptide sequence-ASN-X-(SER/THR)-has been investigated. Of 7 proteins tested, 2 (ovine prolactin and rabbit muscle triosephosphate isomerase) could be enzymatically glycosylated by a particulate preparation from hen oviduct. The remaining 5 proteins, assayed as either S-carboxymethylated or S-aminoethylated derivatives, were inactive as carbohydrate acceptors. However, cyanogen bromide treatment of 2 of the inactive proteins, bovine catalase and concanavalin A from jack bean, yielded peptide fragments which served as substrates for glycosylation. These results suggests that for some proteins, disruption of the tertiary structure is sufficient to allow attachment of carbohydrate. Other denatured proteins may possess additional restrictions imposed by their secondary structure. In certain cases, these restrictions are removed when the polypeptide chain is fragmented.
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PMID:Enzymatic conversion of proteins to glycoproteins by lipid-linked saccharides: a study of potential exogenous acceptor proteins. 73 7

Using the cDNA coding for the human interferon alpha/beta receptor (IFNAR), the IFNAR gene has been physically mapped relative to the other loci of the chromosome 21q22.1 region. 32,906 base pairs covering the IFNAR gene have been cloned and sequenced. Primer extension and solution hybridization-ribonuclease protection have been used to determine that the transcription of the gene is initiated in a broad region of 20 base pairs. Some aspects of the polymorphism of the gene, including noncoding sequences, have been analyzed; some are allelic differences in the coding sequence that induce amino acid variations in the resulting protein. The exon structure of the IFNAR gene and of that of the available genes for the receptors of the cytokine/growth hormone/prolactin/interferon receptor family have been compared with the predictions for the secondary structure of those receptors. From this analysis, we postulate a common origin and propose an hypothesis for the divergence from the immunoglobulin superfamily.
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PMID:The structure of the human interferon alpha/beta receptor gene. 137 Aug 33

Recent studies have demonstrated the importance of prolactin (PRL) and growth hormone (GH) in the regulation of 25-hydroxycholecalciferol-1 alpha-hydroxylase activity. We have previously shown that 1 alpha,25-dihydroxycholecalciferol (1 alpha,25-(OH)2D3) reduces PRL and GH production by a clonal strain of rat pituitary tumour cells (GH3). The biologically active form of vitamin D3, 1 alpha,25-(OH)2D3, acts via an initial binding to cytoplasmic receptor proteins in target cells, and we demonstrate in this study the presence of specific receptors for 1 alpha,25-(OH)2D3 in the GH3 cells. GH3 cell cytosol was incubated with [3H]1 alpha,25-(OH)2D3 at 0-4 degrees C. Maximal binding was obtained between 2 and 6 h, and Scatchard analysis showed one single class of binding sites with Kd of 0.33 +/- 0.05 nM (mean + SD) and a Bmax of 103 +/- 26 fmol/mg cytosol protein. Competitive binding experiments revealed the following potency order: 1 alpha,25-(OH)2D3 greater than 25-OHD3 greater than 1 alpha-OHD3, 24,25-(OH)2D3. In contrast, corticosterone, testosterone, progesterone and oestradiol showed negligible ability to displace [3H]1 alpha,25-(OH)2D3 from its receptor. Sucrose gradient ultracentrifugation in high salt concentration revealed that GH3 cell cytosol possessed at 3.7S [3H]1 alpha,25-(OH)2D3 receptor protein which was inactivated by heating and protease treatment, but not after incubation with DNase or RNase. The receptor protein aggregated in salt-free sucrose gradients since the 3.7S complex was shifted reversibly to a approximately 6S form. Isoelectric focussing localized most of the [3H]1 alpha,25-(OH)2D3 to a protein peak with an isoelectric point of approximately 6 (pI 5.8-6.2). Since this 1 alpha,25-(OH)2D3 receptor protein has similar properties as the corresponding 1 alpha,25-(OH)2D3 receptors found in normal rat tissues, we suggest that lactotropes and somatotropes represent true target cells for 1 alpha,25-(OH)2D3.
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PMID:Demonstration and characterization of a 1 alpha,25-(OH)2D3 receptor-like macromolecule in cultured rat pituitary cells. 300 10

Native disulphide-bonded prolactin (band III) was distinguished from reduced prolactin (band II) and intermediate unstable disulphide-linked conformations by: (a) faster mobility of the former in sodium dodecyl sulphate/polyacrylamide gel electrophoresis, and (b) high-pressure liquid chromatography analyses of tryptic-digested peptides derived from prolactin in various conformations during its refolding pathway from reduced, unfolded to native conformation. The electrophoretic separation has been used to examine the state of disulphide bonding in newly synthesised prolactin translated from bovine pituitary mRNA in a rabbit reticulocyte translation system supplemented with nuclease-treated dog pancreatic microsomal membranes. The formation of correct disulphide pairing in prolactin (band III), synthesised in the in vitro translation system in the presence of pancreatic microsomes, required the presence of a thiol oxidant such as oxidised glutathione during the translation. The action of thiol oxidants on the in vitro biosynthesised and microsomally processed prolactin were both dose-dependent and catalytic; non-thiol oxidants such as NAD+ and NADP+ were ineffective. Examination of the time course of addition of oxidised glutathione to translating lysates showed that efficient and correct disulphide pairing in newly biosynthesised prolactin occurred when the oxidant was present co-translationally, but much lower yields of correctly disulphide-bonded prolactin were obtained when the oxidant was added after translation and processing were complete. The presence of protein-disulphide isomerase in dog pancreatic microsomes, employed in the in vitro translation system to process preprolactin, was demonstrated by (a) two-dimensional polyacrylamide gel electrophoresis of the membrane proteins, and (b) enzymic activity to accelerate reactivation of scrambled ribonuclease. Protein-disulphide isomerase activity was latent in intact microsomal vesicles, full activity being expressed upon sonication. A procedure has been devised to prepare pancreatic microsomal vesicles depleted of protein-disulphide isomerase which are active in processing and segregating in vitro biosynthesised prolactin. These membranes in the presence of low concentrations of oxidised glutathione are less active but in the presence of saturating levels of oxidised glutathione are fully competent in forming correct disulphide bridges in newly synthesised prolactin.
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PMID:Studies on the formation of intrachain disulphide bonds in newly biosynthesised bovine prolactin. Role of protein-disulphide isomerase. 406 47

Epithelial tubulogenesis is responsible for the exquisitely intricate organization of functional units of parenchymal organs. We have previously demonstrated that hepatocyte growth factor (HGF--also known as scatter factor) is a stroma-derived epithelial morphogen, which induces tubulogenesis by kidney-derived epithelial cells in vitro. The mammary gland provides a particularly attractive model for the study of epithelial morphogenesis, since its development in postnatal life involves elongation and branching of epithelial tubules. The aim of the present studies was to assess the expression and modulation of HGF and its receptor c-Met in the rat mammary gland during pregnancy, lactation, and involution. By ribonuclease protection assay, we demonstrate that levels of both HGF and c-met transcripts are progressively reduced during pregnancy, are virtually undetectable during lactation, and increase during the phase of involution to prepregnancy levels. The reduction in HGF and c-met expression corresponds to periods in which functions other than tubulogenesis predominate in the mammary gland, namely alveologenesis (mid to late pregnancy) and milk protein synthesis (lactation). Using a murine mammary gland-derived epithelial cell line, we demonstrate that levels of c-met mRNA are significantly reduced by exogenously added prolactin, providing a possible explanation for the reduction in c-met in the rat mammary gland during lactation. The potential significance of down-regulation of HGF/c-met during lactation is discussed.
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PMID:Modulation of hepatocyte growth factor and c-met in the rat mammary gland during pregnancy, lactation, and involution. 762 35

The effect of prolactin on the digestive potency of the acinar pancreas was examined in pituitary-grafted hyperprolactinemic mice, because our previous experiment showed that a marked proliferation of pancreatic acinar cells was induced by pituitary grafting in mice. To know whether the digestive function is modified, the tissue contents of pancreatic digestive enzymes, such as chymotrypsin, lipase alpha-amylase and ribonuclease, were measured in the hyperprolactinemic mice. Pituitary grafting significantly increased the contents of chymotrypsin and lipase in the pancreas on day 12 after the operation without affecting intake of food, when compared to those in the sham-operated controls. On day 30, however, the differences between pituitary-grafted and control mice were no more discernible. Thus, the digestive enzyme activities are easily modified soon after the increase of circulating prolactin level. This effect of prolactin on the function of the pancreas may be responsible for "homeorhetic" control of nutrients during lactation. In another set of experiments in adrenalectomized-castrated or castrated mice, pituitary grafting induced an increase in the weight of the pancreas. In addition, adrenalectomy in combination with castration did not alter the pancreatic contents of chymotrypsin and lipase but decreased the amylase content. These results taken together seem to indicate that the effect of prolactin on the exocrine pancreas is not mediated by gonadal and adrenal steroid hormones.
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PMID:Modification of pancreatic digestive function by pituitary grafting in mice. 765 48

There have been many reports on radioisotopic in situ hybridization (ISH) studies for the demonstration of pituitary hormone mRNAs in normal pituitary gland and pituitary adenomas. Recent studies have revealed that non-radioisotopic ISH has several advantages over the radioisotopic method. Using ISH with biotinylated oligonucleotide probes, we have been able to localize various pituitary hormone mRNAs in paraffin wax or frozen sections of rat normal pituitary gland and human pituitary adenomas. For control studies we used ISH with sense probes, ISH without probes, pretreatment with ribonuclease, ISH with a probe for beta-actin and Northern blot hybridization. Using biotinylated probes, gene transcripts of rat growth hormone and prolactin were detected by Northern blot hybridization. The same biotinylated probes were used not for light microscope ISH but also for the electron microscopical demonstration of rat growth hormone and prolactin mRNAs on the polysomes of the rough endoplasmic reticula. It is emphasized that biotinylated oligonucleotide probes are useful for the analysis of pituitary endocrine function because they are applicable to the three hybridization methods, namely, Northern blot hybridization and ISH at the light and electron microscope levels.
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PMID:Application of biotinylated oligonucleotide probes to the detection of pituitary hormone mRNA using northern blot analysis, in situ hybridization at the light- and electron-microscope levels. 788 87

Experiments were designed to examine whether vasoactive intestinal polypeptide (VIP), a known stimulator of basal prolactin (PRL) secretion, regulates PRL gene expression in the rat diethylstilbestrol (DES)-induced prolactinoma model. The VIP-induced increase in PRL release could result from increased PRL synthesis and/or decreased PRL degradation. Male Fischer 344 rats were implanted with 10 mg DES pellets 40 or 110 days prior to obtaining the anterior pituitary glands for cell dispersal. Cells were incubated in 1:10 normal rabbit serum or VIP antiserum (AVIP). After incubation, cells were pelleted, washed, and pooled for total nucleic acid extraction. The rat PRL (rPRL) mRNA abundance was quantitated using a solution hybridization/ribonuclease protection assay. Supernatant was collected and analyzed for PRL content using radioimmunoassay. Results from this experiment reveal partial immunoneutralization of intrapituitary VIP significantly decreased PRL secretory rate by rapid reduction in rRPL mRNA in the 40-day tumors. However, in the 110-day tumors the rPRL mRNA steady-state levels were unchanged but the basal release of PRL continued to be decreased by AVIP. These results indicate VIP exerts its effects on PRL secretion through at least two mechanisms.
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PMID:Vasoactive intestinal polypeptide antiserum affects rat prolactin mRNA in 40-day but not 110-day diethylstilbestrol-induced prolactinoma tissue. 803 86

Salmon have been shown to express alternatively spliced IGF-I mRNA transcripts coding for four different IGF-I prohormones. These transcripts, now designated Ea-1, Ea-2, Ea-3 and Ea-4, differ in size due to the inclusion of additional sequences in the E domain-coding region of the molecule. In this study, the tissue distribution and hormonal regulation of expression of alternatively spliced IGF-I mRNA transcripts were investigated in coho salmon. IGF-I mRNAs were detected by solution hybridization/RNase protection assay in all tissues examined. GH treatment significantly increased hepatic IGF-I mRNA content. Hepatic IGF-I mRNA levels were not influenced by prolactin or somatolactin. Heart, fat, brain, kidney, spleen and ovary IGF-I mRNA levels were not affected by GH, prolactin or somatolactin. Ea-1, Ea-3 and Ea-4 mRNA transcripts were detectable in the liver, and Ea-1 and Ea-3 levels increased dramatically in response to GH treatment, whereas the amount of Ea-4 mRNA was unchanged. Most non-hepatic tissues expressed only the Ea-4 transcript, and expression was not influenced by GH, prolactin or somatolactin. Ea-1 and Ea-3 transcripts were visible in gill samples from fish treated with GH. The ovaries of juvenile fish expressed Ea-1, Ea-2 and Ea-4. The amounts of these transcripts were not changed by gonadotrophin treatment. During smoltification of juvenile coho salmon, liver and gill IGF-I mRNA levels increased with increasing plasma GH and thyroxine concentrations. Muscle, brain and ovary IGF-I mRNA levels were unchanged during this period. These data suggest that the liver is a major site of IGF-I production in response to GH. Heart, fat, brain, kidney, spleen and ovary did not show increased IGF-I mRNA levels in response to GH treatment. GH and prolactin had inconsistent effects on muscle IGF-I mRNA levels. Somatolactin and a gonadotrophin preparation did not stimulate IGF-I expression in tissues of juvenile fish. Differences in tissue GH responsiveness can be partially explained by the expression of alternatively spliced IGF-I mRNAs. Of the four hepatic IGF-I mRNA transcripts, Ea-1 and Ea-3 are GH-responsive, while Ea-2 and Ea-4 are not. Most non-hepatic tissues express only the Ea-4 transcript, and IGF-I mRNA levels do not increase after GH treatment. The increased IGF-I mRNA levels observed in gill tissue during smoltification suggest that other factors, in addition to GH, may regulate IGF-I expression.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Differential expression and hormonal regulation of alternatively spliced IGF-I mRNA transcripts in salmon. 818 11


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