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)

The molecular mechanisms by which GH regulates insulin-like growth factor (IGF-I) gene expression remain obscure. One difficulty has been the lack of established GH-responsive cell lines that express the IGF-I gene. To develop such a cell line, we used rat C6 glioma cells which, as determined by RNase protection assay, express the IGF-I gene but not the GH receptor gene. To confer GH responsiveness, C6 cells were cotransfected with vectors that express the GH receptor (pRc/CMV WTrGHR) and Jak2 (pRc/CMV Jak2). GH responsiveness was demonstrated using luciferase reporter genes containing either the Sis-inducible element from the c-fos gene (pTK81-SIE-Luc) or 6 copies of the GH-responsive GAS-like element (GLE) from the rat spi2.1 gene (pSpi-GLE-Luc). The SIE is activated by binding of STAT1 and 3, whereas the GLE binds STAT5. In cells cotransfected with pRc/CMV WTrGHR, pRc/CMV Jak2, and either pTK81-SIE-Luc or pSpi GLE-Luc, treatment with 500 ng/ml GH for 24 h stimulated a 3.1- and 1.7-fold increase in luciferase activity, respectively. These data suggest that in C6 cells cotransfected with pRc/CMV WTrGHR and pRc/CMV Jak2, GH activates STAT1, 3, and 5. To determine whether GH-responsive IGF-I promoter activity could be demonstrated, C6 cells were cotransfected with pRc/CMV WTrGHR, pRc/ CMV Jak2, and an IGF-I-luciferase fusion gene that contained a fragment of the rat IGF-I gene that extended from -412 in the 5'-flanking region of exon 1 to the Met-22 in exon 3. GH stimulated a modest, but reproducible, 1.7-fold increase in luciferase activity in these cells, suggesting that a GH-responsive element is present in this region of the IGF-I gene. To better localize the GH-responsive element, cells were cotransfected with pRc/CMV WTrGHR, pRc/CMV Jak2 plus one of several IGF-I-luciferase fusion genes containing either fragments of one of the two promoters in the IGF-I gene or a fragment of intron 2 that includes a GH-responsive DNase I hypersensitivity site. For all constructs, treatment with GH for 24 h did not stimulate a significant increase in luciferase activity, suggesting that GH-responsive sequences are not located in these specific regions of the IGF-I gene or that GH-directed transcription of the IGF-I gene is mediated via several different regions of the IGF-I gene and the effect of any one of these regions in isolation was not sufficiently robust to be detected in this model system. In summary, transient expression of the GH receptor and Jak2 in C6 cells creates a GH-responsive system that activates STAT1, 3, and 5. Moreover, a fragment of the IGF-I gene that contains exons 1 and 2, a fragment of exon 3, and introns 1 and 2 is GH responsive using this model system.
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PMID:Growth hormone-mediated regulation of insulin-like growth factor I promoter activity in C6 glioma cells. 1038 99

Several studies have suggested that testosterone may have a direct, GH-independent effect on growth. In order to assess possible mechanism(s) whereby testosterone exerts its growth-promoting effect, we evaluated its effect on growth mediators of the GH-IGF-I axis, in both the liver and the epiphyseal growth plate (EGP). Testosterone was administered to peripubertal rats and the responses of mRNA of GH receptor, IGF-I, IGF-I receptor and IGF-binding proteins-1 and -3 (IGFBP-1 and IGFBP-3) as well as circulating IGF-I were evaluated in two time-related models: over 12 h after a single injection (short-term study) and 10 days after continuous administration (long-term study). Rats in the short-term study were castrated and were killed 1, 4, 6 and 12 h post injection. Rats in the long-term study were divided into two groups: castrated vs castrated and hypophysectomized, in order to assess the effect of testosterone in the presence and absence of GH. mRNA levels were determined by RNase protection assay, and serum IGF-I by RIA. Testosterone enhanced weight gain in the rats treated for 10 days, a change that was similar in the presence or absence of GH. This effect was relatively small, however, by comparison with the total weight gained without testosterone. Testosterone had no effect on hepatic IGF-I mRNA abundance but induced a reduction in circulating IGF-I levels, in both the short- and long-term study. Testosterone had no effect on hepatic GH receptor and IGFBP-3 mRNA levels but resulted in a transient, short-term elevation in IGFBP-1 mRNA levels that was maximal 4 h post injection. In the EGP, neither testosterone administration nor hypophysectomy had any effect on IGF-I and IGF-I receptor mRNA levels. However, testosterone increased GH receptor mRNA abundance after 10 days of continuous administration in hypophysectomized rats only. These data suggest that the effect of testosterone on growth (as assessed by weight gain) is small and is not mediated by changes in hepatic gene expression of IGF-I, IGF-I receptor, IGFBP-1, IGFBP-3 or circulating IGF-I. At the EGP, the testosterone effect on linear growth is not mediated through changes in mRNA abundance of IGF-I and IGF-I receptor. The small but significant elevation of GH receptor mRNA levels in hypophysectomized rats may suggest a testosterone-mediated augmentation of a GH effect at the target organ.
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PMID:Testosterone effect on growth and growth mediators of the GH-IGF-I axis in the liver and epiphyseal growth plate of juvenile rats. 1051 58

Mutations within the growth hormone receptor (GHR) gene that lead to an inactivated or truncated GHR protein cause abnormal growth and small adult size in a variety of species (Laron dwarfism). We studied a line of miniature Bos indicus cattle that have phenotypic (small mature size) and endocrine (increased blood growth hormone and decreased blood insulin-like growth factor-I concentrations) similarities to Laron dwarfs. Liver mRNA from miniature and control cattle was used to amplify a cDNA within the coding region of the GHR. The miniature cattle had GHR mRNA size (determined by Northern blot) and cDNA sequence that were similar to control cattle and, therefore, were unlike most Laron dwarf genotypes in which the GHR gene is mutated. Amounts of mRNA from liver as well as muscle (superficial neck and longissimus) were analyzed by ribonuclease protection assay for IGF-I, total GHR, GHR 1A (inducible, liver-specific GHR mRNA), and GHR 1B (constitutive GHR mRNA). Four control and five miniature bulls were tested. As expected, liver IGF-I mRNA was decreased in the miniature cattle (approximately 12% of control; P < 0.01). The amount of the total GHR as well as GHR 1A mRNA were also decreased in liver (17% and 19% of control, respectively; P < 0.01). Other GHR mRNA, including GHR 1B mRNA, were similar for miniature and control cattle. In muscle, there was a tendency (P < 0.10) for decreased IGF-I mRNA and increased GHR mRNA in miniature compared with control cattle. In summary, a novel phenotype for Laron dwarfism in Bos indicus cattle was associated with underexpression of GHR 1A mRNA, but not other GHR mRNA variants in liver. In addition to decreased GHR 1A mRNA, the miniature cattle had decreased liver IGF-I mRNA. Full expression of GHR 1A in liver, therefore, may be required for full liver IGF-I expression and normal growth.
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PMID:A novel phenotype for Lardon dwarfism in miniature Bos indicus cattle suggests that the expression of growth hormone receptor 1A in liver is required for normal growth. 1062 32

We studied whether programmed cell death (or apoptosis) is the predominant mechanism in radiation-induced cell damage to rat intestinal mucosa and investigated the mechanism of the protective effect of GH and IGF-I in the same model. Male albino Wistar rats were divided into four groups: controls, radiation, radiation plus GH and radiation plus IGF-I. Radiation was administered on the first day and on day 4. All animals were sacrificed and segments of the terminal ileum were stained with hematoxylin-eosin. Apoptosis of the epithelial cells was identified at the cellular level by the TUNEL stain and was distinguished from necrosis by the characteristic morphology of the cells (cytoplasmic shrinkage, marginal chromatin condensation and generation of nuclear apoptotic bodies). Apoptotic cells in the control animals were few and detected only at the tips of the villi while in the irradiated animals almost all the epithelial cells were apoptotic, distributed from the crypts to the tips of the villi and the mucosa showed severe epithelial atrophy and ulceration. The histologic picture of the mucosa in the GH and IGF-I treated animals was similar to normal controls and apoptotic cells were restricted only at the tips of the villi. DNA and RNA from the mucosa cells were isolated and analyzed by electrophoresis. DNA fragmentation and RNA 28s band ribonuclease cleavage was observed only in the irradiated animals. We have shown that abdominal radiation causes intestinal epithelial cell damage mainly through the induction of apoptosis and the treatment with GH and IGF-I inhibits apoptosis of the cells and preserves the mucosal integrity.
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PMID:Growth hormone and insulin-like growth factor I protect intestinal cells from radiation induced apoptosis. 1071 45

The extent to which the local somatotrophic axis is functional in extrahepatic tissues in the neonate is unclear. We therefore determined the expression of growth hormone (GH) receptor (GHR), and insulin-like growth factors I and II (IGF-I and IGF-II) mRNA in liver and skeletal muscle (longissimus) of neonatal pigs given daily intramuscular injections of either recombinant porcine GH (1 mg/kg body wt; n = 6) or saline (n = 5) for 7 days. Exogenous GH increased plasma concentrations of GH 30-fold and IGF-I threefold. Abundances of specific mRNA in liver and muscle were measured by RNase protection assays (values are arbitrary density units). In liver, GH treatment increased GHR (6.0 vs. 9.7; P < 0.01) and IGF-I (5.2 vs. 49.0; P < 0.001) but not IGF-II (19.5 vs. 17.2) mRNA. In muscle, GH treatment increased IGF-I mRNA (13.3 vs. 22.8; P < 0.05) but not GHR (8.3 vs. 9.5) or IGF-II (16.1 vs. 16.9). These results demonstrate that exogenous GH can induce local somatotrophic function predominantly in liver but also in muscle of newborn pigs. Our novel finding on the selective increase in muscle IGF-I but not GHR gene expression suggests differences in posttranscriptional regulation and/or intracellular signaling mechanisms.
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PMID:Exogenous growth hormone induces somatotrophic gene expression in neonatal liver and skeletal muscle. 1074 70

Ovarian follicular growth and steroidogenesis are controlled by the interaction of insulin-like growth factors (IGFs) and gonadotropins. The objective was to determine the temporal and spatial relationships for gonadotropin receptor, steroidogenic enzyme, and IGF system gene expression during the development of preovulatory porcine follicles. Sows (n = 18) were weaned and follicles were monitored by transrectal ultrasonography. Ovaries were collected from sows when the mean diameter of the preovulatory follicular cohort was approximately 2, 4, 6, or 8 mm. mRNA were measured by in situ hybridization for individual follicles within the preovulatory cohort (3 to 5 follicles per sow). Patterns of gene expression detected by in situ hybridization were confirmed by RNase protection analyses of pooled RNA samples. The amount of LH receptor mRNA and steroidogenic enzyme mRNA (17alpha-hydroxylase and aromatase) increased as the mean diameter of the follicular cohort increased from 2 to 6 mm, but then decreased abruptly for 8-mm follicles. Estradiol concentrations in follicular fluid closely followed the expression patterns of steroidogenic enzymes and LH receptor mRNA. FSH receptor mRNA was present in cohorts of 2-mm follicles but declined in 4-mm follicles and was undetectable in 6- and 8-mm follicles. The expression of IGF-I and type I IGF receptor mRNA were similar for follicles of 2, 4, 6, and 8 mm. In contrast, IGF-II mRNA progressively increased in follicles collected from 2-, 4-, and 6-mm cohorts, and then decreased slightly at 8 mm. Type II IGF receptor mRNA was greatest in 8-mm follicles. IGF binding protein-2 (BP-2) mRNA decreased as follicles achieved progressively larger sizes during the preovulatory period (2 to 8 mm), whereas the IGFBP-4 mRNA remained relatively low for follicles in 2- to 6-mm cohorts but then increased markedly in 8-mm follicles. In summary, temporal and spatial patterns of gene expression for gonadotropin receptor, steroidogenic enzyme, and IGF system genes were characterized in preovulatory porcine follicles by using in situ hybridization and RNase protection analyses. The unique patterns of gene expression suggest interdependence among specific genes that may be essential for preovulatory follicular development.
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PMID:Growth and the initiation of steroidogenesis in porcine follicles are associated with unique patterns of gene expression for individual componentsof the ovarian insulin-like growth factor system. 1095 42

A growing body of information documents the existence of a complete rat intrafollicular insulin-like growth factor (IGF)-I system replete with a ligand (IGF-I), a receptor (type 1 IGF receptor) IGF binding proteins (4 and 5), and IGFBP-directed endopeptidases (4 and 5). Previous studies have established the ability of IGF-I to promote the elaboration of granulosa cell-derived IGFBP-5 and to suppress the activity of granulosa cell-derived IGFBP-5-directed endopeptidase. It was the purpose of this article to examine the effects of treatment with IGF-I on the other components of the intrafollicular IGF system, i.e., IGF-I itself and the type 1 IGF-receptor. Granulosa cells, obtained by follicular puncture from 25-d-old estrogen-primed rats were cultured in polystyrene tubes for 72 h under serum-free conditions, in the absence or presence of the indicated agents. At the conclusion of each experiment, media were discarded, and RNA was extracted and subjected to an RNase protection assay. Treatment of cultured rat granulosa cells with IGF-I resulted in a significant 1.8-fold increase in the steady-state levels of IGF-I mRNA. No effect was noted on the total cellular DNA content thereby arguing against the possibility that the relative increase in IGF-I transcripts can be ascribed to a possible treatment-induced increase in cell number in culture. The IGF-I effect was apparent (p < 0.05) at IGF-I doses as low as 1 ng/mL, minimal additional increments being noted thereafter. Treatment with insulin and des (1-3) IGF-I proved equally effective, producing 2.0- and 2.6-fold increases, respectively, thereby suggesting that the IGF-I effect may be mediated via the type 1 IGF receptor. Treatment with IGF-I also resulted in a significant (p < 0.005) increase in type 1 IGF receptor expression (2.3-fold increase), the first significant effect being noted at the 30 ng/mL dose level. Similar results obtained for insulin and des (1-3) IGF-I thereby suggest that the ability of IGF-I to upregulate the expression of its own receptor is probably type 1 IGF receptor-mediated. Taken together, these findings indicate that treatment of estrogen-primed granulosa cells with IGF-I will result in upregulation of the steady-state levels of transcripts corresponding to IGF-I itself and to its type 1 IGF receptor. These observations emphasize the importance of positive autoregulatory phenomena as determinants of the intrafollicular content of IGF-I and its receptor.
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PMID:Insulin-like growth factor (IGF)-I stimulates IGF-I and type 1 IGF receptor expression in cultured rat granulosa cells: autocrine regulation of the intrafollicular IGF-I system. 1105 Oct 53

Although brain injury induced by undernutrition during early life is well described, the mechanisms that mediate the effects of undernutrition on brain development are not known. IGF-I plays an important role in the stimulation of postnatal somatic and brain growth. We have shown that IGF-I overexpression in brain ameliorates the effects of undernutrition on early postnatal brain growth, and thus, we postulated that alterations in IGF-I expression or action mediate the pathogenesis of malnutrition-induced brain injury. To begin to address this issue we evaluated the influence of undernutrition on brain IGF-I expression during early postnatal development in mice. Undernutrition was induced in mice by separating half of the pups in each litter from their lactating dams for a defined period each day. Pups were killed at postnatal day (P) 7, P14, P21, and P28. The changes in IGF-I mRNA were quantified by ribonuclease protection assay. At P7 IGF-I mRNA abundance in undernourished animals was increased in cerebral cortex (223% of controls), but decreased in diencephalon (36% of controls). At P14, IGF-I mRNA abundance was increased in diencephalon (230% of controls). Although there were no other statistically significant alterations of IGF-I mRNA in undernourished mice, IGF-I abundance in the cerebral cortex appeared increased at P14 (142% of controls), and in cerebellum it was consistently but modestly decreased (78 and 59% of controls) from P7 to P21, respectively. We conclude that nutrition regulates murine brain IGF-I expression in a developmentally specific fashion that is dependent on the region of expression. Importantly, the influence of undernutrition on IGF-I expression is markedly different in the brain than in liver, where nutritional deficiency profoundly decreases IGF-I expression. We speculate that the relative preservation of or increases in regional brain IGF-I expression explain, at least in part, the well-known finding that undernutrition during early postnatal development has less marked growth-retarding effects on the brain than it does on the soma.
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PMID:Nutritional regulation of IGF-I expression during brain development in mice. 1115 13

Insulin-like growth factor (IGF)-I and its binding protein IGF binding protein 5 (IGFBP-5) were highly expressed in inflamed and fibrotic intestine in experimental Crohn's disease. IGF-I induced proliferation and increased collagen synthesis by smooth muscle cells and fibroblasts/myofibroblasts in vitro. Here we studied IGF-I and IGFBP-5 in Crohn's disease tissue. Tissue was collected from patients undergoing intestinal resection for Crohn's disease. IGF-I and IGFBP-5 mRNAs were quantitated by RNase protection assay and Northern blot analysis, respectively. In situ hybridization was performed to localize mRNA expression, and Western immunoblot was performed to quantitate protein expression. IGF-I and IGFBP-5 mRNAs were increased in inflamed/fibrotic intestine compared with normal-appearing intestine. IGF-I mRNA was expressed in multiple cell types in the lamina propria and fibroblast-like cells of the submucosa and muscularis externa. IGFBP-5 mRNA was highly expressed in smooth muscle of the muscularis mucosae and muscularis externa as well as fibroblast-like cells throughout the bowel wall. Tissue IGFBP-5 protein correlated with collagen type I (r = 0.82). These findings are consistent with a mechanism whereby IGF-I acts on smooth muscle and fibroblasts/myofibroblasts to increase collagen synthesis and cellular proliferation; its effects may be modulated by locally expressed IGFBP-5.
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PMID:Insulin-like growth factor I and insulin-like growth factor binding protein 5 in Crohn's disease. 1129 12

While transforming growth factor-beta1 (TGF-beta1) regulates proliferation and differentiation of human osteoblast precursor cells, the mechanisms underlying these effects are not known. Several hormones and locally acting growth factors regulate osteoblast functions through changes in the insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs). Thus, we studied the effects of TGF-beta1 on IGFs and IGFBPs in human marrow stromal (hMS) osteoblast precursor cells. TGF-beta1 increased the steady-state mRNA level of IGF-I up to 8.5+/-0.6-fold (P<0.001) in a dose- (0.1-10 ng/ml), and time-dependent (12-72 h) manner. No significant effects on IGF-II gene expression were detectable. Employing RNase protection and nuclear run-on assays, these effects on IGF-I were found to take place at the transcriptional level and were not dependent on de novo protein synthesis. Using the transient transfection of various fragments of the IGF-I promoter 1, we found that TGF-beta responsive elements were present in a promoter fragment ranging from-65 bp to+55 bp relative to the major transcription start site in exon 1. In addition, TGF-beta1 treatment resulted in a dose- and time-dependent increase (2-fold) in the IGFBP-3 steady-state mRNA level as well as in protein production but did not affect IGFBP-2 or IGFBP-4 at mRNA or protein levels. Our results indicate that TGF-beta1 exerts significant effects on stimulatory components of the IGF-system and that may represent a mechanism mediating TGF-beta effects on the biological functions of osteoblasts.
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PMID:Transforming growth factor-beta1 stimulates the production of insulin-like growth factor-I and insulin-like growth factor-binding protein-3 in human bone marrow stromal osteoblast progenitors. 1137 25


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