Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.5 (RNase)
 17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated the ability of dehydroepiandrosterone (DHEA) to alter the production of interleukin-2 (IL-2) and to bind to a specific binding complex in antiCD3 epsilon activated T cells. Binding activity correlated with the presence of a specific DHEA binding complex in the cytosol and nuclei of DHEA-responsive T-cell hybridomas, as well as in CD4+ and CD8+ cells isolated from peripheral lymph nodes of normal mice. Scatchard analysis determined that intact lymphocytes and cytosolic fractions contained high affinity binding for [3H]DHEA (approx. 2.6 nM) with 1000-7000 binding sites existing per cell. Five of the T-cell hybridomas tested both responded to DHEA treatment with increased production of IL-2 and also contained specific high affinity [3H]DHEA binding. Four additional T-cell hybridomas were found to contain no specific [3H]DHEA binding and were also unresponsive to DHEA influences on IL-2 production. Sucrose density gradients demonstrated a 3-4s [3H]DHEA binding complex in high salt and a 7-8s binding complex in low salt. Specific binding was inhibited by preincubation of the cytosol fractions with either trypsin or chymotrypsin, or by heating to 60 degrees C for 1 h (less than 15% of control). [3H]DHEA binding was unaffected by preincubation of the cytosol fractions with ribonuclease, deoxyribonuclease, or phospholipase A. The DHEA-protein complexes bound to DNA-cellulose with the amount of binding being slightly increased by preincubation at 25 degrees C as compared to 4 degrees C. As expected, [3H]DHEA binding was inhibited by the addition of unlabeled DHEA, but was also modestly inhibited by dihydrotestosterone and cortisol. Binding of DHEA was unaffected by progesterone, dexamethasone, estradiol, androsterone, DHEAS, and beta-etiocholanolone at all concentrations tested. DHEA was incapable of inhibiting the binding of [3H]DHT to the androgen receptor or [3H]dexamethasone to the glucocorticoid receptor. Collectively, these findings suggest that murine T cells contain a specific DHEA receptor. We believe that DHEA is a steroid hormone that is directly involved in the regulation of IL-2 production by both normal and some T-cell hybridomas.
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PMID:The presence of a dehydroepiandrosterone-specific receptor binding complex in murine T cells. 135 1

In studies with a synthetic androgen, R 1881, an androgen-binding component was found in the cytosol of human placental villi. Kinetic analysis indicated that the Kd value of this component was 1.4 nM at 0-4 degrees C and that binding of R 1881 amounted to 277 +/- 73 fmol/mg protein. glycerol density gradient ultracentrifugation showed a peak of binding activity in the 8S region in a medium of low ionic strength, but in the 4.5S region in a medium containing 9.5 M KCl. The R 1881-binding component was inactivated by mild heat- or trypsin-treatment, but not by treatment with DNase or RNase. Most of the R 1881-binding activity was sedimented at 20 to 40% saturation of ammonium sulfate. These findings indicate that the R 1881-binding component in human placental cytosol is quite similar in its characteristics to androgen receptors, which are present in various androgen-responsive organs. Testosterone was a more potent competitor of R 1881-binding than DHT or cyproterone acetate. Scatchard plots indicated that the binding site of testosterone was identical with that of R 1881. These findings suggest that the androgen receptor in placental cytosol is specific for testosterone. The Kd value for testosterone was calculated to be 3.2 nM.
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PMID:Androgen receptor in human placental villi. 697 Dec 89

Progression to hormone-refractory disease is a common outcome of human prostate cancer. In this study, we have investigated the basis of androgen insensitivity in the human prostate cancer cell line, PC-3, which was derived from a bone metastasis of a hormone-refractory prostate cancer. PC-3 cells with virtually undetectable (PC-3AR-) or low (PC-3AR+) levels of androgen receptor (AR) RNA expression were examined. RNase protection assays demonstrated that the level of AR RNA in PC-3AR+ cells was similar to that in a normal androgen-responsive genital skin fibroblast cell strain. Quantitative immunocytochemical staining of AR in PC-3AR+ cells using antibodies directed against the amino and carboxyl termini of the receptor revealed staining in 30% of cells with either antibody. Furthermore, the level of AR staining in PC-3AR+ cells was higher than in the androgen-responsive breast cancer cell lines ZR-75-1, T47-D, and MCF-7. Despite the expression of AR RNA and protein, PC-3AR+ cell proliferation was unaffected by the presence of 0.1-10 nM mibolerone. Scatchard analysis demonstrated a complete absence of specific [3H]dihydrotestosterone ([3H]DHT) binding to PC-3AR+ cytosolic extracts, which could not be explained by structural alterations in the AR gene. The sizes of individual AR exons amplified from genomic DNA derived from PC-3AR+ cells were identical to those amplified from normal human cells. Furthermore, sequence analysis did not reveal a mutation in the DNA- or hormone-binding domains of the AR gene in PC-3AR+ cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Evidence for a novel mechanism of androgen resistance in the human prostate cancer cell line, PC-3. 779 9

To determine possible cellular mechanisms governing androgen action in the brain, we examined the hormonal regulation of androgen receptor (AR) mRNA in neural tissues by Northern blot hybridization and RNase protection analysis. While a single hybridizable species of AR mRNA of approximately 11 kb was found in the anterior pituitary gland (AP) and ventral prostate gland (VP), an additional species of AR mRNA, approximately 2 kb smaller, was revealed in neural tissues. Furthermore, in these neural tissues, hormonal regulation of the two species of mRNA was coordinated; long-term castration increased levels of both forms, while testosterone replacement reduced them. The same pattern of regulation was observed for the single 11 kb form in the AP. An RNase protection assay was validated and utilized to quantitatively analyze the hormonal regulation of AR mRNA. Castration (4 days) resulted in significantly increased AR mRNA in the AP and hypothalamic-preoptic area, but not the amygdala, which subsequent administration of dihydrotestosterone (DHT; 1 day; 2 mg/animal) significantly decreased. In the AP, administration of estradiol benzoate (EB) for 1 or 5 days also reversed this effect. However, EB treatment increased the amount of total RNA isolated per gland. Consequently, when the data are normalized to RNA content per gland, 5 days of EB treatment resulted in a significant increase in AR mRNA content. These findings suggest that in contrast to the AP and VP, two forms of androgen receptor mRNA exist in the brain. In addition, there appears to be tissue and hormone specific regulation of AR mRNA.
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PMID:Hormonal regulation of androgen receptor mRNA in the brain and anterior pituitary gland of the male rat. 836 43

In recent years, the enzymes which are involved in the formation of DHT in steroid target tissues have been well investigated, however, enzymes responsible for the catabolism and elimination of steroids in these tissues, in particular the uridine diphospho-glucuronosyltransferase (UGT) family of enzymes, have received much less attention. We have recently demonstrated that human and monkey are unique in having high plasma levels of C19 steroid glucuronides. These circulating conjugates have been proposed to reflect the peripheral conversion of adrenal and gonadal C19 steroids to potent androgens, especially DHT. In humans, the presence of steroid UGT activities is found in the liver and several extrahepatic tissues including the prostate, mammary gland and ovary. In addition, UGT activities were observed in breast and prostate tumor cell lines such as MCF-7 and LNCaP, respectively. In agreement with the presence of steroid conjugating enzymes in extrahepatic tissues, UGT cDNA clones, which encode steroid conjugating proteins, have been isolated from libraries constructed from human and monkey prostate mRNA. The presence of UGT transcripts and proteins in extrahepatic tissues in both species, as determined by Northern blot, ribonuclease protection, specific RT-PCR, in situ hybridization, Western blot and immunocytochemistry analysis, indicate the relevance of steroid glucuronidation in tissues other than the liver. Knowing that both the human prostate and the human prostate cancer LNCaP cell line express steroid metabolizing proteins, including UGT enzymes, regulation of UGT mRNA and protein levels, as well as promoter activity was studied in these cells. The results demonstrate a differential regulation between the two highly related isoforms UGT2B15 and UGT2B17, where only the expression of UGT2B17 was affected following treatments of LNCaP cells with androgens, growth factors or cytokines. Steroid conjugation by UGT enzymes is potentially involved in hormone inactivation in steroid target tissues, thus modifications in UGT expression levels may influence hormonal responses.
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PMID:Characterization of UDP-glucuronosyltransferases active on steroid hormones. 1041 20

The 3'UTRs of mammalian HIF-1alpha and EGF mRNA contain several highly conserved AU-rich elements (ARE) known to control the turnover of labile mRNAs by binding ARE-binding proteins that regulate nucleocytoplasmic shuttling, translation, and degradation. Androgens regulate the level and subcellular shuttling of HuR, a major ARE-binding protein that stabilizes many ARE-mRNAs. Pull down of biotinylated 3'UTRs of HIF-1alpha or EGF enriches HuR on blots from Jurkat cell lysates 5-fold, and enriches the amount of RNase-protected biotinylated RNA that comigrates with HuR approximately 10-fold. Dihydrotestosterone treatment decreases the HuR-protected riboprobe pulled down from total Jurkat cell lysates by 30-40%, apparently reflecting shifts in HuR from the nucleus to the cytoplasm. Androgen treatment also changes the amount of HuR-protected riboprobe pulled down from a PC-3 clone expressing a functional androgen receptor. The shift in the amount of riboprobe bound by HuR suggests that androgen is up-regulating endogenous ARE-mRNAs that can compete for binding endogenous HuR. These changes in the shuttling and ARE-binding of endogenous HuR indicate that androgen can act posttranscriptionally to regulate ARE-mRNAs, including HIF-1alpha and EGF.
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PMID:Androgens regulate the binding of endogenous HuR to the AU-rich 3'UTRs of HIF-1alpha and EGF mRNA. 1532 78