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:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The insulin-like growth factor (IGF)-II/mannose-6-phosphate (M6P) receptor, which targets acid hydrolases to lysosomes, is a multifunctional protein with separate binding sites for IGF-II and M6P. The purpose of this study was to determine if alveolar macrophages (AM) and their precursor cells, blood monocytes, expressed this receptor. AM expressed IGF-II/M6P receptors as detected by [125]IGF-II surface binding that was not reduced by recombinant IGF-I or IGF-I receptor monoclonal antibody (alpha IR3). Surface binding was also detected on blood monocytes and could be upregulated approximately 4-fold by incubation with lipopolysaccharide. There were no differences in surface binding by AM lavaged from individuals with asbestos exposure or from normal volunteers. Using the polymerase chain reaction and reverse transcriptase to reverse-transcribe mRNA from mononuclear phagocytes, specific IGF-II/M6P receptor cDNA was amplified and detected by agarose gel electrophoresis from both AM and blood monocytes. The IGF-II/M6P receptor has an intracellular transport role in many cells cycling from the cell surface to the cytoplasm, or binding to phosphorylated acid hydrolases in the Golgi and transporting them to an acidic prelysosomal site where they dissociate and fuse to the lysosomes and IGF-II/M6P recycles to the trans-Golgi. These functions may be particularly important in asbestosis and other interstitial lung diseases where AM are activated, intracellular lysosomes are a prominent morphologic feature, and acid hydrolases are found in recovered lavage fluid.
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PMID:Human mononuclear phagocytes express the insulin-like growth factor-II/mannose-6-phosphate receptor. 164 80

The insulin-like growth factor (IGF) system is thought to function as a mediator of steroid hormone actions in the endometrium. IGFs (IGF-I and IGF-II) are also potent mitogens in endometrial cancer. The biological actions of IGFs are modulated by specific binding proteins (IGFBP)--6 cloned and sequenced so far--which may either inhibit or enhance the effects of IGF at the cellular level. In the endometrium, IGFBP-1 gene expression is stimulated by progesterone and inhibited by insulin, while IGFBP-1 inhibits the mitogenic action of IGF-I. In this study, we used a quantitative reverse transcriptase polymerase chain reaction (RT-PCR) to investigate IGFBP-1, IGFBP-2, IGFBP-4, IGFBP-5 and IGFBP-6 gene expression in endometrial cancer tissues. Endometrial cancer tissue samples were collected from 20 women (aged 54-79 yrs) with stage I to II well-differentiated endometrial adenocarcinoma. Samples of normal endometrium (n = 14) obtained from women undergoing tubal ligation in various phases of the menstrual cycle, and normal early-pregnancy endometrium (decidua) were studied for comparison. In endometrial cancer tissues, the IGFBP-1 mRNA was undetectable or minimally expressed when studied by RT-PCR. The mean (+ SD) levels of IGFBP-2 and IGFBP-4 and IGFBP-5 mRNAs in endometrial cancer tissues did not differ from those in normal endometrium, in which no cyclic variation was observed, suggesting that the genes encoding IGFBP-2, IGFBP-4 and IGFBP-5 are not hormonally regulated in the endometrium. The IGFBP-6 mRNA expression showed a significant cyclic variation in normal endometrium, with low levels in late-proliferative and early- to mid-secretory phases and high expression in late-secretory and early-proliferative phases. In endometrial cancer tissues, the mean IGFBP-6 mRNA level was similar to that in cycling endometrium during the peri-ovulatory period. In summary, a continuous stimulation of the endometrial epithelial cells by IGFs with suppressed IGFBP-1 expression may lead to an imbalance in the IGF system of the endometrium and trigger an uncontrolled cell proliferation, ultimately resulting in malignant transformation.
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PMID:Suppressed expression of insulin-like growth factor binding protein-1 mRNA in the endometrium: a molecular mechanism associating endometrial cancer with its risk factors. 752 16

Ovulation rate, serum hormone concentrations, follicular fluid (FFL) concentrations of steroids and IGF, IGF binding protein (IGFBP) activity in FFL, and follicular IGF-I and -II mRNA were compared during the follicular phase among five genotypes of ewes: Finn (F), Composite III (C), 1/2 Booroola Merino (B) x 1/2 F (B x F), 1/2 F x 1/2 C (F x C), 1/2 B x 1/2 C (B x C). Composite III ewes were a Columbia x Suffolk x Hampshire crossbred. Ovulation rates for F (n = 7), C (n = 5), B x F (n = 6), F x C (n = 3), and B x C (n = 8) ewes were 3.1, 1.6, 3.8, 2.9, and 2.9 (Pooled SEM = .5), respectively. Concentrations of IGF-I in FFL were 53% greater (P < .05) in large (> or = 4.1 mm) than in small (< 4.1 mm) follicles but did not differ (P > .10) among genotypes. In contrast, FFL IGF-II concentrations were greater (P < .05) in B x C and B x F ewes than in C or F x C ewes but did not differ between small and large follicles. Ligand blotting revealed that IGFBP activity of three species (34, 27 to 29, and 24 kDa) were lower (P < .05) in FFL of large than in FFL of small follicles but did not differ (P < .10) among genotypes. Follicular wall IGF-I mRNA and IGF-II mRNA was detected in 5 and 32% of the samples from preovulatory follicles, respectively, using reverse transcriptase-PCR and ethidiumbromide staining. Ovarian IGF-I mRNA levels, assessed by Northern analysis, in B x F and B x C ewes were greater (P < .05) than those in C ewes; ovarian IGF-I mRNA levels in F and F x C ewes were intermediate and did not differ (P > .10) from those in C ewes. Small follicles from B x C and B x F ewes had severalfold greater (P < .05) estradiol concentrations than those from F or C ewes, whereas large follicles from B x F ewes had twice (P < .05) the estradiol concentrations of follicles from F or C ewes. Progesterone in FFL did not differ among genotypes. Serum LH, FSH, inhibin, IGF-I, and progesterone did not differ (P > .10) among genotypes.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Serum hormones, follicular fluid steroids, insulin-like growth factors and their binding proteins, and ovarian IGF mRNA in sheep with different ovulation rates. 754 85

Insulin-like growth factors I (IGF-I) and II (IGF-II) are anabolic for osteoblastic cells. Although expression of IGF-I and IGF-II mRNA has been demonstrated in rodent osteoblastic cells, little is known about IGF gene expression in human osteoblastic cell models. In this study we characterized IGF-I and -II mRNA expression in (1) normal human osteoblast-like (hOB) cells, (2) a simian virus 40 immortalized hOB (HOBIT) cell line, and (3) human osteosarcoma cell lines SaOS-2, TE-85, MG-63, and U-2. Since cross-hybridization of IGF cDNA probes with ribosomal RNA obscures detection of some of the multiple IGF transcripts in human cells, we replaced Northern analysis with the more specific ribonuclease protection assay (RPA). We also used the reverse transcriptase-polymerase chain reaction (RT-PCR) to assess whether mRNAs were present at trace levels. IGF-I mRNA expression was consistently observed in normal hOB cells only and by both RT-PCR and RPA. Among IGF-I transcript variants, Ea IGF-I mRNA was more abundant than the Eb mRNA in normal hOB cells. Trace levels of IGF-I mRNA were variably detected in SaOS-2 and U-2 osteosarcoma cells when RT-PCR was performed, but we found no IGF-I mRNA in HOBIT, TE-85, or MG-63 cells. IGF-II mRNA was expressed in normal hOB, HOBIT, TE-85, and U-2 cells as assessed by either method.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Normal human osteoblast-like cells consistently express genes for insulin-like growth factors I and II but transformed human osteoblast cell lines do not. 763 14

The expression of insulin-like growth factors and their binding proteins in normal human peripheral lymphocytes was studied using the reverse transcriptase polymerase chain reaction method and Western ligand blotting. A quantitation of RT-PCR products was used to study the differences between normal and PHA stimulated lymphocytes. Normal freshly collected lymphocytes expressed mRNAs for both IGF-I receptor and IGF-II receptor but no expression of the corresponding growth factors was detectable. After stimulation with phytohemagglutinin the lymphocytes, however, expressed both IGF-I and IGF-II. Of the five IGFBPs examined, unstimulated lymphocytes expressed only IGFBP-2 and -3. Stimulated lymphocytes expressed IGFBP-4 and -5, in addition to IGFBP-2 and -3, whereas IGFBP-1 mRNA remained undetectable. The ligand blotting of lymphocyte conditioned media revealed production of 34K, 43K and 49K IGFBPs. The addition of estrogen, progesterone, IGF-I or growth hormone did not affect secretion of IGFBPs by lymphocytes.
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PMID:The expression of insulin-like growth factors and their binding proteins in normal human lymphocytes. 768 Aug 35

The ovine insulin-like growth factor-II (oIGF-II) gene is comprised of 9 exons that span approximately 25 kb. Approximately 750 nucleotides upstream of oIGF-II exon 1 are the three exons of the ovine insulin gene that are transcribed in the same direction as oIGF-II. The genomic organization and expression of the oIGF-II gene is similar to that of the human IGF-II gene. Four putative promoters direct the transcription of six 5' noncoding exons (1, 3, 4, 5, 6, and 7), which are alternatively spliced to the shared exons 8, 9, and 10. An ovine exon comparable to human exon 2 has not been identified. Multiple transcription initiation sites were identified for exons 1 and 6 by primer extension analysis. Using a reverse transcriptase polymerase chain reaction (RT-PCR) assay, exon 1 and 3 transcripts were shown to be expressed in adult but not fetal liver. In addition, a novel transcript, which contained exon 1 spliced directly to exon 8, was detected in adult liver. Exon 4 transcripts were not detected in either fetal or adult liver, whereas exon 6 and 7 transcripts were detected in both fetal and adult liver. Exon 5 transcripts were also expressed in both fetal and adult liver, which is in contrast to the tumor cell-specific expression of human exon 5. Like the human and rodent genes, the regulation of expression of the oIGF-II gene is under complex control.
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PMID:Characterization of the linked ovine insulin and insulin-like growth factor-II genes. 801 Nov 64

Recent studies suggest that brain ependyma and choroid plexus produce neuropeptide processing enzymes. To facilitate the understanding of these cells and their ability to produce biologically active peptides, we developed cultures of defined cell type. Ependymal cells were characterized by morphological criteria, and choroid plexus epithelial cell lines were characterized by the presence of the mRNA for IGF-II and transthyretin, a thyroxine binding protein produced in liver and choroid plexus. The ependymal cells and the choroid plexus epithelial cell lines were then examined for the presence of mRNAs for various neuropeptide processing enzymes. Northern blot analysis revealed high levels of furin, carboxypeptidase E, and peptidyl glycine alpha-amidating monooxygenase mRNAs, with levels in ependymal cells comparable to those in brain or pituitary. Carboxypeptidase E activity was detected in medium from cultured ependymal cells; this activity was identified as carboxypeptidase E based on the acidic pH optimum and sensitivity to various inhibitors. The mRNAs for other neuropeptide processing enzymes, such as prohormone convertases 1 and 2, were not detected on Northern blots of RNA from ependyma or choroid plexus epithelium. Since ependyma and choroid plexus epithelium express a subset of processing enzymes, we suggest that these cells have the capacity to produce biologically active peptides. Initial screening by reverse transcriptase-polymerase chain reaction assays has demonstrated the presence of mRNA for the neurosecretory proteins chromogranin B and secretogranin II in both ependyma and choroid plexus epithelium.
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PMID:Expression of neuropeptide processing enzymes and neurosecretory proteins in ependyma and choroid plexus epithelium. 840 52

Insulin and insulin-like growth factors (IGF-I and -II) are members of a family of growth factors which are known to be developmentally regulated during preimplantation mouse embryogenesis. The physiological actions of the insulin family of growth factors are mediated by interactions with specific cell surface receptors that are detectable on the cells of preimplantation mouse embryos. Mouse embryonic stem (ES) cells are totipotent cells derived directly from the inner cell mass of the blastocyst. ES cells have the ability to differentiate into all three germ layers and have unlimited growth potential under certain culture conditions. The great advantage of ES cells is the ability to obtain large amounts of tissue for biochemical studies as compared with preimplantation embryos. To examine in greater detail the biological actions of the insulin family of growth factors, the expression of their cognate receptors on ES cells was examined. ES cells were cultured in DMEM medium supplemented with leukemia inhibitory factor (LIF) to maintain the undifferentiated state. Receptor expression was evaluated at the mRNA level using the reverse transcription polymerase chain reaction (RT-PCR), and at the protein level by radioactive labeled ligand-receptor binding assay. Using RT-PCR, mRNAs of all three growth factor receptors were detected in ES cells. Messenger RNA from ES cells was reverse transcribed into cDNA by AMV reverse transcriptase at 42 degrees C for 1 hr. The reverse transcription reaction was amplified with Taq polymerase and specific primers for insulin, IGF-I, or IGF-II receptors by PCR. RT-PCR and the control plasmid cDNA PCR products were resolved electrophoretically on 3% agarose gels. Each amplified PCR product showed the predicted correct size.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mouse embryonic stem cells express receptors of the insulin family of growth factors. 856 62

Insulin-like growth factors IGF-I and IGF-II are potent inducers of oligodendrocyte development. Because IGF-I is produced, in some cases, by the same cells that respond to it (autocrine/paracrine action), we examined the possibility that IGF-I is expressed by developing oligodendroglial cells. We employed a sensitive method, reverse transcriptase-polymerase chain reaction (RT-PCR), to detect IGF-I mRNA in purified populations of oligodendroglial cells isolated from rat brain during the period of oligodendrocyte development. Cells were purified by fluorescence activated cell sorting (FACS), using antibodies to the cell surface antigenic markers O4 and galactocerebroside (GC). RNA was isolated from the sorted cells, reverse-transcribed, and PCR-amplified, using a strategy that recognizes IGF-I mRNA but not DNA. The amplified band was identified as IGF-I by size, hybridization to an IGF-I-specific antisense probe, and restriction analysis. IGF-I mRNA was detected in O4-positive/GC-negative oligodendrocyte precursors and, more weakly, in GC-positive oligodendrocytes. IGF-I mRNA could be detected reproducibly in RNA extracted from 100-cell samples of O4-positive cells, making it unlikely that the mRNA was derived from contaminants in the FACS-sorted cell populations. We conclude that IGF-I is expressed by developing oligodendroglia. Autocrine expression of IGF-I by developing oligodendroglial cells suggests that oligodendrocyte development is, in part, autoregulatory.
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PMID:Developing oligodendroglia express mRNA for insulin-like growth factor-I, a regulator of oligodendrocyte development. 856 38

Production of insulin-like growth factor binding protein (IGFBP)-2 and accumulation of IGFBP-2 mRNA was determined in six leukaemic T-, B- or promyelocytic cell lines. Cell growth was compared in serum free medium M-3 and in medium M-9 containing 5% FCS. In both media, high amounts of IGFBP-2 as measured by radioimmunoassay were detectable in culture supernatant of T-cell lines and promyelocytic HL-60 cells, whereas only small amounts of IGFBP-2 were secreted by the B-cell lines. Production of IGFBP-2 in M-9 was approximately 20-fold higher (up to 195 ng ml-1) than in M-3, partially reflecting higher proliferation. However, quantitative reverse transcriptase polymerase chain reaction analysis revealed that, independent of the culture medium 10(6) T-cells contained between 30 and 48 units IGFBP-2 mRNA relative to the glycerol aldehyde phosphate dehydrogenase control gene, but B-cells contained less than 1 unit. Since IGF-II is known to be a major regulator of IGFBP-2, its influence on IGFBP-2 expression has to be investigated.
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PMID:Insulin-like growth factor binding protein 2 is differentially expressed in leukaemic B- and T-cell lines. 889 48


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