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)

Since animal models of human immunodeficiency virus (HIV) infection are being used increasingly in determining various aspects of virus/host interaction and as models for virus expression, it will be important to assess any significant differences in anti-viral immune responses between animals and humans. Previous studies have shown that incubation of HIV with non-immune sera from several animal species results in virus neutralization, and that rabbit serum can lyse HIV-infected cells. The objectives of the current study were to evaluate the animal complement pathway(s) activated by HIV and HIV-infected cells and determine the mechanism by which complement could mediate viral neutralization. Incubation of HIV-infected cells with mouse, guinea-pig or rabbit sera resulted in cell-surface deposition of C3 fragments. Deposition of C3 fragments did not occur either in the presence of C4-deficient guinea-pig serum or in the absence of Ca2+, indicating that activation by infected cells occurred via the classical pathway. Neutralization of free virus was also mediated by the classical pathway since C4-deficient guinea-pig serum and Ca(2+)-chelated sera lacked activity. Serum treatment of virus resulted in release of HIV reverse transcriptase (RT), suggesting that neutralization occurred by C5b-9-mediated virolysis. RT was also released from simian immunodeficiency virus by animal complement. Antibodies in animal sera were not responsible for the classical pathway activation by free virus or HIV-infected cells. These results define several substantial differences between animal and human complement reactivity with HIV which could significantly affect the ability of HIV to replicate in animals, and which need to be considered in the assessment of animal models of HIV infection.
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PMID:Human immunodeficiency virus (HIV)-infected cells and free virus directly activate the classical complement pathway in rabbit, mouse and guinea-pig sera; activation results in virus neutralization by virolysis. 191 89

The chronically infected promonocytic clone U1 expresses low-to-undetectable constitutive levels of human immunodeficiency virus (HIV). Virus replication in these cells can be increased up to 25-fold by phorbol esters (phorbol-12-myristate-13-acetate), recombinant cytokines such as tumor necrosis factor-alpha, and cytokine-enriched mononuclear cell supernatants. We have tested specific activators of protein kinases (PK) and PK inhibitors (isoquinolinesulfonamide derivatives), as well as calcium-mobilizing agents, for their effect on constitutive and induced virus expression in U1 cells. Virus expression was measured by reverse transcriptase, Western blot, and nuclear run-on analysis. Activation of PKC by 1-oleyl,2-acetylglycerol, a synthetic analog of the natural ligand 1,2-diacylglycerol, and bryostatin 1 (a recently described specific PKC activator) resulted in a two- to eightfold increase in virus production. In contrast, activators of cyclic-nucleotide-dependent PKs were not effective in inducing virus expression. PK inhibitors were tested for their effect on HIV upregulation by cytokines and other inducing agents. The isoquinolinesulfonamide derivative H7, a potent inhibitor of PKC activation, effectively blocked (70 to 90%) HIV induction by cytokines and phorbol-12-myristate-13-acetate. The derivative HA1004, which is more selective for cyclic-nucleotide-dependent kinases, did not suppress viral induction. In addition, increases in intracellular calcium levels dramatically enhanced HIV production induced by both specific PKC activators and cytokines. These results indicate that activation of PKC is a common pathway involved in the upregulation of HIV expression in chronically infected cells stimulated by cytokines and other inducing agents.
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PMID:Direct and cytokine-mediated activation of protein kinase C induces human immunodeficiency virus expression in chronically infected promonocytic cells. 220 Aug 85

Using the calcium-phosphate procedure the plasmid cDm2055, which carries the copia transposable element of Drosophila melanogaster, was co-transfected with the Neor-carrying plasmid pSVCneo-1 into the D. hydei cell line KUN-DH-33 which was free of copia. The Neor transfectants stably carried both plasmids as tandem oligomers integrated in the chromosome and virus-like particles (VLP) were produced specifically in the transfectants that received the copia plasmid. The particles were quite similar in various aspects such as size, morphology, density, RNA content and molecular weight of the major protein component, to retrovirus-like particles (RVLP) that spontaneously appear in cultured cells of D. melanogaster: the reverse transcriptase activity however seemed to be low compared to that of the D. melanogaster RVLP. This finding demonstrates that the retrovirus-like particles (RVLP) in Drosophila cultured cells are produced by the transposable genetic element copia resident in the host chromosomes.
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PMID:Production of virus-like particles by the transposable genetic element, copia, of Drosophila melanogaster. 243 82

The gap between early molecular evolution and the origin of the first cell may have been bridged by a photoheterotrophic obcell, consisting of genes and ribosomes attached to the outer surface of a phospholipid vesicle containing a light-driven proton pump and a proton-driven pyrophosphate synthase. I argue that the obcell was the substratum for the origin of DNA replication; DNA segregation by the growth and division of the peptidoglycan murein; periplasmic solute-binding proteins; bioenergetics, including the F0F1 proton-driven ATP synthase; active transport of calcium; and facilitated diffusion of nutrients across membranes, and that it played the major role in the replacement of ribozymes by protein catalysts. Curved growth of the peptidoglycan and a mutation causing septum formation produced the first true cell. Evolution of porins, sodium extrusion and potassium import, conversion of the facilitated diffusion proteins to active pumps, and the evolution of intermediary metabolism, carbon and nitrogen fixation, and of substrate level phosphorylation, completed the origin of the first negibacterial eubacterium, from which all other cells evolved, and from which they have inherited most of their major catalytic properties--with the notable exceptions of reverse transcriptase, RNA splicing, and methanogenesis, all of which I believe evolved very much later.
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PMID:The origin of cells: a symbiosis between genes, catalysts, and membranes. 345 90

Exposure in vitro of various mammalian retroviruses to the chelating agents EDTA or EGTA in millimolar concentrations resulted in partial disintegration of viral membranes as measured by accessibility or even release of reverse transcriptase, an internal viral protein, without any other treatment usually required. Among the viruses responding to chelators were mammalian type C viruses, primate type D viruses and bovine leukemia virus. The effect was dose-dependent. The avian type C virus AMV, however, was found to be not susceptible to the agents. Rauscher mouse leukemia virus treated in vitro with EDTA or EGTA showed reduced infectivity in mice. The results are considered as evidence for some association of divalent cations with membranes of mammalian retroviruses. The disintegrating activity of EGTA suggests that Ca2+ is an integral constituent of viruses but Mg2+ may also be involved. These cations seem to be responsible for maintaining integrity of retroviral membranes which, after chelation of ions, are either disrupted or become permeable for the exogenous template of reverse transcriptase. In addition, the disintegrating activity of trifluoperazine may indicate that a calmodulin-like protein occurs in retroviral membranes.
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PMID:Disintegration of retroviruses by chelating agents. 681 93

Osteoblasts express calcium channels that are thought to be involved in the transduction of extracellular signals regulating bone metabolism. The molecular identity of the pore-forming subunit (alpha 1) of L-type calcium channel(s) was determined in rat osteosarcoma UMR-106 cells, which express an osteoblast phenotype. A homology-based reverse transcriptase-polymerase chain reaction cloning strategy was employed that used primers spanning the fourth domain. Three types of cDNAs were isolated, corresponding to the alpha 1S (skeletal), alpha 1C (cardiac), and alpha 1D (neuroendocrine) isoforms. In the transmembrane segment IVS3 and the extracellular loop formed by the IVS3-S4 linker, a single pattern of mRNA splicing was found that occurs in all three types of calcium channel transcripts. Northern blot analysis revealed an 8.6-kb mRNA that hybridized to the alpha 1C probe and 4.8- and 11.7-kb mRNAs that hybridized to the alpha 1S and alpha 1D probes. Antisense oligonucleotides directed to the calcium channel alpha 1D transcript, but not those directed to alpha 1S or alpha 1C transcripts, inhibited the rise of intracellular calcium induced by parathyroid hormone. However, alpha 1D antisense oligonucleotides had no effect on the accumulation of cAMP induced by parathyroid hormone. When L-type calcium channels were activated with Bay K 8644, antisense oligonucleotides to each of the three isoforms partially inhibited the rise of intracellular calcium. The present results provide evidence for the expression of three distinct calcium channel alpha 1-subunit isoforms in an osteoblast-like cell line. We conclude that the alpha 1D isoform is selectively activated by parathyroid hormone.
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PMID:Multiple calcium channel transcripts in rat osteosarcoma cells: selective activation of alpha 1D isoform by parathyroid hormone. 747 9

We tested the hypothesis that adrenomedullin (ADM), a recently isolated hypotensive peptide, is an autocrine transmitter in renal arterial smooth muscle cells (RASMCs). Fura-2 fluorometry revealed that ADM decreases both the cytosolic Ca2+ concentration ([Ca2+]i) and tension induced by 0.3 microM phenylephrine (PE) in porcine RASMCs. The expression of ADM mRNA in RASMCs was assessed by the reverse transcription polymerase chain reaction (RT-PCR), using the total RNA from the RASMCs and the specific primers for the porcine ADM mRNA. A band with an expected size could be detected only when the reverse transcriptase was added, thus indicating that the porcine RASMCs express ADM mRNA. These results therefore suggested that ADM plays an important role in the regulation of the renal vascular tone, not only as a circulating hormone, but also as an autocrine transmitter.
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PMID:Autocrine regulation of the renal arterial tone by adrenomedullin. 748

Nitric oxide (NO) has effects on renal blood flow, glomerular filtration rate, renin secretion, and renal sodium excretion. Four isoforms of nitric oxide synthase (NOS) have been cloned to date. However, the molecular identity of NOS present in the renal vasculature is unknown. Endothelial NOS (NOS-III) is regulated both acutely by cell calcium and chronically by shear stress. To determine if renal blood vessels and the glomerulus express NOS-III mRNA, we used degenerate polymerase chain reaction (PCR) to clone a portion of rat NOS-III. We then assayed NOS-III mRNA in microdissected renal structures by reverse transcriptase-PCR. NOS-III mRNA was expressed at high levels in glomeruli, arcuate vessels, and interlobular artery/afferent arterioles. NOS-III mRNA was detected inconsistently in proximal tubules, thick ascending limbs, and cortical and inner medullary collecting ducts. Previous studies have shown that chronic oral treatment with the NOS inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) decreases NO synthesis and causes hypertension. To determine if the systemic blockade occurs only by competitive inhibition, we determined the effect of L-NAME on glomerular NOS-III mRNA. L-NAME administration (5 days) decreased NOS-III mRNA in the glomerulus to 25 +/- 12% of control levels. We conclude that endothelial NOS-III mRNA is preferentially expressed in the glomerulus and renal vasculature, where it can modulate renal blood flow and glomerular filtration rate. Furthermore, glomerular NOS-III may be modulated at the level of mRNA abundance in vivo by systemic L-NAME.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Localization and regulation of endothelial NO synthase mRNA expression in rat kidney. 752 Jun 68

Human umbilical vein endothelial cells have recently been shown to respond to C5a with increases in intracellular Ca2+, production of D-myo-inositol 1,4,5-triphosphate and superoxide anion generation. In the current studies, C5a had been found to cause in a time- and dose-dependent manner rapid expression of endothelial P-selectin, secretion of von Willebrand factor, and adhesiveness for human neutrophils. The effects of C5a in P-selectin expression and adhesiveness of neutrophils were similar to the effects of histamine and thrombin on endothelial cells. The adhesiveness of C5a-stimulated endothelium for neutrophils was blocked by anti-P-selectin, but not by antibodies to intercellular adhesion molecule 1, E-selectin, or CD18. A cell-based ELISA technique has confirmed upregulation of P-selectin in endothelial cells exposed to C5a. Binding of C5a to endothelial cells has been demonstrated, with molecules bound being approximately 10% of those binding to neutrophils. By a reverse transcriptase-PCR technique, endothelial cells have been shown to contain mRNA for the C5a receptor. These data suggest that C5a may be an important inflammatory mediator for the early adhesive interactions between neutrophils and endothelial cells in the acute inflammatory response.
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PMID:C5a-induced expression of P-selectin in endothelial cells. 752 84

CD30L, the ligand for the activation antigen CD30, is a member of the tumor necrosis factor family of cytokines. Binding of CD30L to CD30, which is a member of the nerve growth factor/tumor necrosis factor receptor family, induces proliferation in peripheral blood lymphocytes and Hodgkin's derived cell lines with a T-cell phenotype such as HDLM-2 and L540, while cell lines derived from anaplastic large cell lymphomas, such as Karpas 299, undergo cell death. In order to investigate whether mutations of the CD30 antigen are responsible for these opposite effects, we cloned the open reading frame of CD30 cDNAs from the cell lines L540 and Karpas 299 and from peripheral blood lymphocytes by reverse transcriptase polymerase chain reaction. Sequencing of independent plasmid clones revealed that these cells have a silent transition (A-->G) at position 771 of the open reading frame compared to the published sequence derived from the HTLV-1+ cell line HUT-102. As published data have shown that crosslinking of CD30 induces an elevation of cytosolic free calcium ([Ca2+]i) in TCR positive Jurkat cells, we have analysed the effect of crosslinking of CD30 on L540 and Karpas 299 cells. No elevations of [Ca2+]i have been observed in these cell lines after crosslinking of CD30 with HRS-4. We conclude (i) that the different functional effects of CD30 in PBL, L540 and Karpas 299 are not due to differences in the primary structure of the receptor; and (ii) that the different responses observed upon engagement with CD30L for the cell lines L540 and Karpas 299 do not correlate with differences in mobilization of [Ca2+]i after crosslinking of CD30.
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PMID:Opposite effects of the CD30 ligand are not due to CD30 mutations: results from cDNA cloning and sequence comparison of the CD30 antigen from different sources. 752 1


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