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

---

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

Seven days after activation with concanavalin A and irradiated spleen cells, murine CD4+ T cells were re-stimulated with ionomycin and phorbol 12-myristate 13-acetate (PMA). IL-2 and IL-4 were determined in the supernatant. When cholera toxin, forskolin together with phosphodiesterase inhibitors or dibutyryl-cAMP were added at the time of re-stimulation, a dose-dependent increase of IL-4 and IL-5 release was noted. IL-2 was down-regulated as reported before. The up-regulation of IL-4 and the down-regulation of IL-2 correlated with an increase of IL-4 mRNA and a decrease of IL-2 mRNA as determined by semi-quantitative reverse transcriptase polymerase chain reaction. Similar results were found with prostaglandin E2 using PMA and ionomycin or plate-bound anti-CD3 antibody as re-stimulants. These results suggest that, in activated CD4+ T cells, cAMP-elevating agents induce a switch of lymphokine production towards a Th2-like phenotype through regulation at the transcriptional level. This is supported by the fact that complex formation between a synthetic nuclear factor of activated T cells (NF-AT) binding site from the IL-2 promoter and nuclear extracts was decreased when cholera toxin was added to re-activated CD4+ T cells, suggesting that cholera toxin and cAMP down-regulate IL-2 expression via decreased NF-AT binding. Finally, since IL-4 has been reported to amplify IL-4 release from activated CD4+ T cells, the autoinduction of IL-4 may very well function via cAMP.
...
PMID:cAMP up-regulates IL-4 and IL-5 production from activated CD4+ T cells while decreasing IL-2 release and NF-AT induction. 781 41

The present study reports the isolation of a cDNA clone that encodes a second member of the corticotropin-releasing factor (CRF) receptor family, designated as the CRF2 receptor. The cDNA was identified using oligonucleotides of degenerate sequence in a PCR paradigm. A PCR fragment obtained from rat brain was utilized to isolate a full-length cDNA from a rat hypothalamus cDNA library that encoded a 411-amino acid protein with approximately 70% identity to the known CRF1 receptor over the entire coding region. When expressed in mouse Ltk- cells, this receptor stimulates cAMP production in response to CRF and known CRF-like agonists. CRF and the nonmammalian CRF-related peptides sauvagine and urotensin I stimulate adenylate cyclase activity in a dose-dependent manner with a rank order of potency different from that of the CRF1 receptor: sauvagine > urotensin > or = rat/human CRF > ovine CRF. Tissue distribution analysis of the mRNAs by reverse transcriptase-PCR shows CRF2 receptor mRNA is present in rat brain and detectable in lung and heart. In situ hybridization studies indicate specific expression within the brain in the ventromedial nuclei of the hypothalamus, the lateral septum, the amygdala, and entorhinal cortex, but there is unremarkable expression in the pituitary. An additional splice variant of the CRF2 receptor with a different N-terminal domain has been identified by PCR, encoding a putative protein of 431 amino acids. Thus, the data demonstrate the presence of another functional CRF receptor, with significant differences in the pharmacological profile and tissue distribution from the CRF1 receptor, which would predict important functional differences between the two receptors.
...
PMID:Cloning and characterization of a functionally distinct corticotropin-releasing factor receptor subtype from rat brain. 784 62

Natriuretic peptides act via receptors with intrinsic guanylate cyclase activity to stimulate cGMP production and are thought to be important regulators of neuroendocrine systems. C-Type natriuretic peptide (CNP) is of particular interest in this regard because the highest tissue concentrations of CNP occur in the anterior pituitary, where it is a highly potent stimulator of cGMP production. Here we show that pituitaries of rats and mice contain abundant CNP prohormone messenger RNA (mRNA), but no atrial natriuretic peptide or B-type natriuretic peptide prohormone mRNAs. Using reverse transcriptase-polymerase chain reaction, both A- and B-type natriuretic peptide receptor (GC-A and GC-B, respectively) transcripts were detected in rat and mouse pituitaries, although only the GC-B mRNA was measurable by Northern blotting. Immunohistochemistry revealed CNP-positive cells in the anterior, but not posterior, pituitaries of rats, and the vast majority of these cells were identified as gonadotropes by colocalization of CNP and LH immunoreactivities. Targeted toxicity using GnRH conjugated to the ricin-A chain was used to test whether gonadotropes are also direct targets for GnRH action. The conjugate dose dependently inhibited the proliferation of alpha T3-1 cells (gonadotrope-derived cells with GnRH receptors), but had no such effect on GH3 cells (which do not have GnRH receptors). Culture of rat pituitary cells with the conjugate caused comparable reductions in CNP-stimulated cGMP production, GnRH-stimulated LH release, and CA2+ ionophore (A23187)-stimulated LH release, but did not measurably alter cAMP production in response to pituitary adenylate cyclase-activating polypeptide. We conclude that CNP is synthesized in the pituitary, where it is located predominantly in gonadotropes, and GC-B receptors expressed in the pituitary mediate the direct effects of CNP in gonadotropes. Together with the recent demonstration of CNP synthesis and action in alpha T3-1 cells, the data suggest CNP to be a novel autocrine regulator of gonadotropes.
...
PMID:C-type natriuretic peptide (CNP) in the pituitary: is CNP an autocrine regulator of gonadotropes? 798 73

Parathyroid hormone-related protein is responsible for the hypercalcaemia caused by many tumours. Measurement of parathyroid hormone-related protein is becoming more accessible with the introduction of commercial assays. We report a case of hypercalcaemia of malignancy secondary to parathyroid hormone-related protein in a woman with renal carcinoma. The parathyroid hormone-related protein was assayed using a new immunoradiometric assay. We demonstrated an initial fall in parathyroid hormone-related protein and calcium levels after surgery and a rise in both before clinical relapse. However, the clinical relapse was itself associated with a fall in serum parathyroid hormone-related protein, nephrogenous cAMP and calcium, suggesting that the tumour had stopped producing parathyroid hormone-related protein or perhaps that post-translational processing had occurred as the tumour advanced. The tumour was investigated for parathyroid hormone-related protein mRNA content using reverse transcriptase polymerase chain reaction, both at diagnosis in surgically removed material, and using post-mortem specimens. The level of parathyroid hormone-related protein mRNA, while present, was much reduced in the recurrent tumour suggesting that active parathyroid hormone-related protein production fell substantially as the tumour advanced. This case suggests that, although demonstration of parathyroid hormone-related protein in hypercalcaemia is useful for diagnosis, tumoral secretion of this product may alter.
...
PMID:Hypercalcaemia due to parathyroid hormone-related protein: long-term circulating levels may not reflect tumour activity. 828 89

By using reverse transcriptase/PCR and oligonucleotide sequences derived from conserved segments (including the conserved RRGDL sequence) of the known proprotein convertases (PCs) PC1, PC2, furin, and PC4, we identified a subtilisin/kexin-like PC called PC5 in both mouse and rat tissues. The composite structure (2.85 kb) was deduced from the analysis of the reverse transcription/PCR products combined with the sequence from a clone isolated from a cDNA library made from corticotropin-activated mouse adrenocortical Y1 cells. The deduced cDNA structures of mouse PC5 and rat PC5 showed that the closest homologue is PACE4. Furthermore, like furin, Drosophila melanogaster (d) dfurin2, and PACE4, PC5 shows the presence of a C-terminal Cys-rich domain containing either 5 (PC5 and PACE4) or 10 (dfurin2) repeats of the consensus motif Cys-Xaa2-Cys-Xaa3-Cys-Xaa(5-7)-Cys-Xaa2-Cys-Xaa (8-15)-Cys-Xaa3-Cys-Xaa(9-16). The richest sources of rat PC5 mRNA (3.8 kb) are the adrenal and gut, but it can also be detected in many endocrine and nonendocrine tissues. Corticotropin-stimulated adrenocortical Y1 cells showed an increased expression of PC5 mRNA, suggesting an upregulation by cAMP. In situ hybridization of rat brain sections demonstrated a unique distribution of PC5 compared to PC1, PC2, and furin.
...
PMID:cDNA structure of the mouse and rat subtilisin/kexin-like PC5: a candidate proprotein convertase expressed in endocrine and nonendocrine cells. 834 87

Although thyrotropin is known to regulate thyroid cell differentiation and proliferation, human thyroid carcinoma cells are relatively insensitive or resistant to TSH stimulation. The expression levels of TSH receptor are significantly lower in carcinoma tissues than in normal tissues. Furthermore, in vitro human thyroid cell growth is not regulated by TSH itself. We, therefore, isolated neomycin-resistant stable human thyroid carcinoma cell (WRO cell) transfectants overexpressing intact human TSH receptor to evaluate the functional role of TSH receptor on carcinoma cells. Southern blot analysis confirmed incorporation and amplification of human TSH receptor complementary DNA sequences into genomic DNA. Northern gel analysis and reverse transcriptase-polymerase chain reaction analysis revealed the presence of specific TSH receptor messenger RNA (4.0 kilobases), and the specific binding and the affinity of [125I]TSH on stably transfected WRO cells were demonstrated compared to wild type. Nevertheless, impaired cAMP production to transfectants by TSH was observed. cAMP production was confirmed after stimulation of both wild type and transfectants by forskolin, cholera toxin, and isoproterenol. In contrast, TSH could affect the cytoplasmic calcium mobilization immediately after the addition of TSH to WRO transfectants. These results suggest that the impairment of TSH action on human thyroid carcinoma cells is not due to a major structural abnormality of the TSH receptor, reduction in the receptor number, or receptor affinity, but much more likely due to a TSH receptor-guanyl nucleotide-binding protein coupling defect.
...
PMID:Overexpression of the intact thyrotropin receptor in a human thyroid carcinoma cell line. 838 Oct 75

D1 dopamine receptors stimulate cAMP accumulation in opossum kidney (OK) cells, but this response is attenuated by pretreatment with dopamine. Dopamine pretreatment also causes a reduction in D1 dopamine receptor number. We transfected OK cells with a rat cAMP phosphodiesterase cDNA (rPDE3) in order to determine the contribution of elevations of cAMP to those two phenomena. Wild-type (WT) OK cells were compared to three clones (C, H, and N) which demonstrated stable expression of the rPDE3 phenotype and genotype, rPDE3 RNA expression was confirmed in clones C, H, and N (but not in WT-OK cells) by reverse transcriptase-polymerase chain reaction. A functional rPDE3 phenotype was demonstrated in that dopamine-responsive cAMP accumulation was absent in clones C, H, and N in intact cells, but could be restored by preincubation with cAMP phosphodiesterase inhibitors, or by using washed membranes from those clones. All three clones had increased cAMP phosphodiesterase activity when compared to WT-OK cells (approximately 100% increase), and blunted or absent dopamine (1 microM)-induced protein kinase A activation. After pretreatment with dopamine (1 microM) for 1 h, clones C, H, and N desensitized equally well as WT-OK cells (approximately 40-50% reduction in maximal increase in cAMP). In contrast, down-regulation of D1 dopamine receptors was blunted for clone C (20% receptor loss) and absent for clones H and N, when compared to a 45% loss of receptors for WT-OK cells. These findings suggest that in OK cells pretreated with 1 microM dopamine (i) cAMP accumulation is not necessary for dopamine-induced desensitization, but (ii) is necessary for down-regulation of D1 dopamine receptors, and (iii) that the down-regulation and desensitization processes may be differentially regulated.
...
PMID:Elevation of cAMP is required for down-regulation, but not agonist-induced desensitization, of endogenous dopamine D1 receptors in opossum kidney cells. Studies in cells that stably express a rat cAMP phosphodiesterase (rPDE3) cDNA. 839 59

Cytomegalovirus (CMV) infection constitutes a serious threat to patients with acquired immune deficiency syndrome. Recently we reported that human immunodeficiency virus (HIV) infection of CD4+ cells was associated with sustained elevation of cellular levels of cAMP. Moreover, cyclic nucleotide modulators enhanced HIV replication by increasing intracellular levels of cAMP. In this study, the effect of CMV on HIV replication in CMV/HIV mixed infection and its relationship to cAMP were examined. MT-4 cells, CMV strain AD169, and HIV strain IIIB were used. Optimal enhancement (4.4-fold increase) of HIV replication was observed when MT-4 cells were infected with CMV at Day 0 followed by HIV on Day 4 after infection, as determined by reverse transcriptase activity on Day 11 after infection. cAMP (measured by radioimmunoassay) levels in cells infected with CMV alone, HIV alone, or CMV/HIV together were 2-, 3-, and 5-fold above untreated cells, respectively. CMV also enhanced the replication of UV-irradiated HIV 4-fold and this was associated with a 2-fold increase in cAMP as well. Moreover, UV-irradiated CMV enhanced HIV replication 8.8-fold. The same dose of viable and UV-irradiated CMV used in the above experiments increased protein kinase C activity in these cells 3.0- and 8.0-fold, respectively. These findings might suggest that cAMP and protein kinase C are involved in CMV enhancement of HIV replication. These findings may have relevance to the identification of novel target sites for development of antiviral therapeutics.
...
PMID:Involvement of cAMP and protein kinase C in cytomegalovirus enhancement of human immunodeficiency virus replication. 841 79

Two cDNA clones homologous with human neuropeptide (NP) Y-Y1 receptor have been isolated from a mouse bone marrow cDNA library. One was thought to be the cognate of the human NPY-Y1 receptor, termed Y1 alpha receptor, and the other form, termed Y1 beta receptor, differed from the Y1 alpha receptor in the seventh transmembrane domain and C-terminal tail. Analysis of the mouse genomic DNA showed that both receptors originated from a single gene. The different peptide sequences of the Y1 beta receptor were encoded by separate exons, hence, these receptors were generated by differential RNA splicing. High affinity binding of [125I]NPY to each receptor expressed in Chinese hamster ovary (CHO) cells and sequestration of [125I]NPY after binding to each receptor were observed. In the CHO cells expressing the Y1 alpha receptor, intracellular Ca2+ increase, inhibition of forskolin-induced cAMP accumulation, and mitogen-activated protein kinase (MAPK) activation were observed by stimulation of NPY, and these responses were abolished by pretreatment with pertussis toxin. Since wortmannin completely inhibited NPY-elicited MAPK activation, we speculate that wortmannin-sensitive signaling molecule(s) such as phosphoinositide 3-kinase may lie between pertussis toxin-sensitive G-protein and MAPK. In contrast, these intracellular signals were not detected in CHO cells expressing the Y1 beta receptor. Northern blots and reverse transcriptase-polymerase chain reaction analyses indicated that the Y1 alpha receptor was highly expressed in the brain, heart, kidney, spleen, skeletal muscle, and lung, whereas the Y1 beta receptor mRNA was not detected in these tissues. However, the Y1 beta receptor was expressed in mouse embryonic developmental stage (7 and 11 days), bone marrow cells and several hematopoietic cell lines. These results suggest that the Y1 beta receptor is an embryonic and a bone marrow form of the NPY-Y1 receptor, which decreases in the expression during development and differentiation.
...
PMID:Identification of two isoforms of mouse neuropeptide Y-Y1 receptor generated by alternative splicing. Isolation, genomic structure, and functional expression of the receptors. 853 Apr 15

The effects of adenosine 3',5'-cyclic monophosphate (cAMP) on cardiac myocyte nitric oxide (NO) production were studied. Maximal nitrite (NO2(-)) production by cultured neonatal rat cardiac myocytes was achieved with 500 U/ml interleukin-1 beta (IL-1 beta) for 48 h (4.6 +/- 0.3 nmol/1.25 x 10(5) cells; n = 12). Cardiac myocytes exposed to 500 U/ml IL-1 beta for 48 h stained positively for inducible nitric oxide synthase (iNOS) by immunohistochemistry. Forskolin (FSK; adenylate cyclase stimulator) or dibutyryl cAMP (DBcAMP; membrane-permeable cAMP analogue) administration alone had no effect on NO2(-) production. The addition of FSK or DBcAMP to IL-1 beta significantly increased NO2-) levels vs. IL-1 beta alone (9.7 +/- 0.6 and 10.9 +/- 0.8 vs. 4.6 +/- 0.3 nmol/1.25 x 10(5) cells per 48 h, respectively; P < 0.01; n = 12). Semiquantitative reverse transcriptase-polymerase chain reaction revealed increased iNOS mRNA in myocytes treated with FSK+IL-1 beta or DBcAMP+IL-1 beta vs. those treated with IL-1 beta alone. The addition of FSK or DBcAMP to IL-1 beta increased iNOS mRNA half-life over IL-1 beta treatment alone (10.6, 11.7 vs. 2.4 h, respectively). Cardiac myocytes do not express iNOS in response to cAMP alone. Rather, cAMP enhances iNOS mRNA stability following cytokine exposure.
...
PMID:cAMP enhances inducible nitric oxide synthase mRNA stability in cardiac myocytes. 859 15


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---