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:2.7.7.48 (transcriptase)
9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have examined the sensitivity of various cellular and viral DNA polymerases to Suramin, an antitrypanosomal drug, which has been reported to exhibit antireverse transcriptase activity. We find that Suramin is a nonspecific inhibitor of all the viral and cellular DNA polymerases, including terminal deoxynucleotidyl transferase, and that the inhibition is most readily reversed by the addition of serum albumin. The drug appears to bind to all the enzyme proteins with no apparent selectivity. Binding of Suramin to enzyme has been found to result in the loss of both substrate and templateprimer binding abilities of various enzymes, confirming the nonspecific nature of protein-Suramin interaction.
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PMID:Observations on the suramin-mediated inhibition of cellular and viral DNA polymerases. 240 17

Proteins that have been modified by long-term expose to glucose accumulate advanced glycosylation end products (AGEs) as a function of protein age. In these studies, we have examined the interaction of AGE-protein with renal cell carcinoma cells (RCC) in vitro, using AGE-modified bovine serum albumin (AGE-BSA) as a probe. AGE-BSA showed tendency to induce in vitro cell growth of RCC cells and promoted the production of interleukin-6 (IL-6), an in vitro autocrine growth factor. Reverse transcriptase-polymerase chain reaction analysis revealed that RCC cells used here express mRNA for a receptor for AGEs (RAGE). These results suggested that AGEs taken up through RAGE on RCC cells might play a role in promoting the growth of RCC cells.
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PMID:Expression of receptors for advanced glycosylation end products on renal cell carcinoma cells in vitro. 824 Mar 77

Previous studies have demonstrated the feasibility of implantation of human blood cells or tissues in lethally irradiated mice or rats, radioprotected with SCID mouse bone marrow cells: The Trimera system. In the present study, we describe the development of a mouse Trimera model for human hepatitis B virus (HBV) infection. In this model, viremia is induced by transplantation of ex vivo HBV-infected human liver fragments. Engraftment of the human liver fragments, evaluated by hematoxylin-eosin staining and human serum albumin mRNA expression, was observed in 85% of the transplanted animals 1 month postimplantation. Viremia levels were determined in these mice by measuring serum HBV DNA using polymerase chain reaction (PCR), followed by dot-blot hybridization. HBV DNA is first detected 8 days after liver transplantation. Viremia attains a peak between days 18 and 25 when HBV infection is observed in 85% of the transplanted animals. The HBV-Trimera model was used to evaluate the therapeutic effects of human polyclonal anti-HBs antibodies (Hepatect) and of two reverse-transcriptase inhibitors, lamivudine (3TC) and beta-L-5-fluoro-2',3'-dideoxycytidine (beta-L-5FddC). Treatment of HBV-Trimera mice with these drugs effectively reduced both the percentage of infected animals and the viral load in their sera. Treatment cessation resulted in rebound of viral load, indicating HBV replication upon drug withdrawal. These results show that the HBV-Trimera model represents a novel experimental tool for simulating human HBV infection and evaluating potential anti-HBV therapeutic agents.
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PMID:The hepatitis B virus-trimera mouse: a model for human HBV infection and evaluation of anti-HBV therapeutic agents. 991 35

Ochratoxin A (OcA) is a prominent member of a group of mycotoxins which display nephrotoxic, genotoxic, teratogenic, carcinogenic and immunosuppressive effects and which have also been linked to Balkan Endemic Nephropathy. The toxicity of OcA is thought to be primarily due to its inhibition of phenylalanine-t-RNA synthetase, a phenylalanine-metabolizing enzyme. Based on the three-dimensional structure of phenylalanine-t-RNA synthetase, we have analyzed its interactions with OcA by means of molecular-dynamical simulations and identified three quite different binding modes, all of which suggest an affinity only in the millimolar range. This would seem to be in conflict with toxicological findings frequently cited in textbooks but is in agreement with recent in vitro studies on purified phenylalanine-t-RNA synthetase, which also exclude this enzyme as the main target for OcA action. In vivo, OcA binds preferentially to serum albumin, a plasma protein, with a corresponding effect on its toxicokinetics (retention). Antagonizing this effect would lead to an enhanced elimination rate, thereby reducing all adverse effects of OcA, as has been demonstrated using albumin-deficient mice. Based on the three-dimensional structure of serum albumin, we have simulated its interaction with OcA. The long-term goal is the animal-free identification of a synthetic antagonist with an affinity between that of the endogenous ligands (e.g. billirubin) and OcA. Such a substance could - by reducing the retention time of the toxin in the body - potentially eliminate all toxic effects of OcA.
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PMID:[Ochratoxins: Molecular strategies for developing an antidote] 1117 22

Thyroglobulin (Tg), has recently been identified as a transcriptional regulator of thyroid-restricted genes. The extrathyroidal expression of several of these genes (including the transcription factor Pax-8) together with the occurrence of specific Tg binding sites suggests a secondary role for Tg as a circulating hormone. In this study, we demonstrate using Northern analysis that Pax-8 is expressed in the mouse mesangial cell, and that its transcript levels are suppressed by Tg. These cells also express an asialoglycoprotein receptor, a receptor involved in Tg endocytosis in the thyroid, and a Tg transcript smaller than the 8.3-kb thyroidal form. Reverse transcriptase PCR showed that suppression of Pax-8 by Tg is correlated with reduced expression of bcl-2 apoptosis suppressor. Tg, but not triiodothyronine (T(3)) significantly increased MC proliferation above control as determined by DNA content of MC cultures. The effect of Tg on proliferation was not duplicated by either bovine serum albumin, gamma-globulins, lactoferrin, or the ASGPR-specific ligand,orosomucoid. These results suggest a possible endocrine role for Tg in regulating both Pax-8 related gene transcription and cell division in the mesangial cell.
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PMID:Thyroglobulin increases cell proliferation and suppresses Pax-8 in mesangial cells. 1145 62

Dysregulated renal water handling is a cardinal feature of nephrotic syndrome that has been shown in animal models of experimental nephrosis to mediate renal aquaporin (AQP) expression. However, data on the effect of proteinuria on the proximal tubule, which is heavily vested with AQP1 and therefore may participate in water homeostasis, are limited. To investigate this, we exposed primary human proximal tubular epithelial cells (PTECs) to two key proteinuric components shown to perturb tubule function: human serum albumin and transferrin. Using reverse-transcriptase polymerase chain reaction and immunocytochemical techniques, PTECs in the quiescent state were found to express AQP3 in addition to AQP1 gene and protein, which was also validated in a human proximal tubule cell line, HK-2. Immunohistochemical staining localized AQP1 synthesis to the apical and basolateral membranes and AQP3 synthesis to the basolateral membrane of proximal tubule epithelium. Transferrin in doses reaching nephrotic range upregulated PTEC transcription and translation of both AQP1 and AQP3 in a time- and dose-dependent manner. After 24 hours of stimulation, transferrin led to a 2.4- and 2.2-fold increase in AQP1 and APQ3 messenger RNA expression, whereas protein synthesis surged by 40.7% +/- 2.48% and 24.2% +/- 0.9% compared with control, respectively. These effects were not observed with albumin challenge and were not caused by osmolality fluctuation with transferrin treatment. In summary, our novel finding of AQP3 in PTECs indicates a role for AQP3 in proximal tubule water reabsorption. The pathophysiological significance of heightened AQP1 and AQP3 expression in PTECs on protein challenge as occurs in the nephrotic state requires further investigation.
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PMID:In vitro studies of aquaporins 1 and 3 expression in cultured human proximal tubular cells: upregulation by transferrin but not albumin. 1147 58

Adynamic bone disease and elevated serum levels of advanced glycation end products (AGEs) often are found in patients with renal failure caused by diabetic nephropathy. To clarify the role of AGEs in adynamic bone disease, we investigated the effect of these substances on cultured human osteoblasts and parathyroid cells. After 72 hours of incubation with AGEs-bovine serum albumin (BSA) (1,000 microgram/mL), there was significant inhibition of the synthesis of type I collagen and osteocalcin in response to stimulation with 10(-10) to 10(-8) M of 1,25-dihydroxycholecalciferol. In a human osteoblastic cell line (MG 63), AGEs-BSA did not affect human osteocalcin promoter activity. In human parathyroid cells, a receptor for AGEs was detected by reverse-transcriptase polymerase chain reaction. Incubation with AGEs-BSA for 48 hours significantly inhibited parathyroid hormone secretion in response to a low calcium concentration of 0.81 mM (P < 0.01). In HEK-293 cells, expressing calcium-sensing receptors, the same AGE concentration caused a significant potentiation of the extracellular Ca(2+) induced-intracellular calcium concentration after 24 and 48 hours of incubation (P < 0.05 and P < 0.01). These data suggest that AGEs are involved in the pathogenesis of adynamic bone disease by inhibiting osteoblastic activity and by inhibiting parathyroid hormone secretion in response to hypocalcemia.
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PMID:Role of advanced glycation end products in adynamic bone disease in patients with diabetic nephropathy. 1157 45

Both innate and adaptive immune systems are thought to participate in the pathogenesis of rheumatoid arthritis in adults and children. The experiments reported here were undertaken to examine how immune complexes, potent stimulators of inflammation, may regulate cells of the adaptive immune system. Human T cells were prepared from peripheral blood by negative selection and incubated with bovine serum albumin (BSA)-anti-BSA immune complexes that were formed in the presence or absence of human C1q. C1q-bearing immune complexes, but not unopsonized complexes, elicited both TNF-alpha and IFN-gamma secretion from human T cells. Secretion of both cytokines was time- and dose-dependent. Cross-linking C1q on the cell surface of T cells produced the same results. Cytokine secretion was not inhibited by blocking the C3b receptor (CR1, CD35) on T cells prior to incubation with immune complexes. Reverse transcriptase polymerase chain reaction (RT-PCR) of immune complex-stimulated cells revealed accumulation of both TNF-alpha and IFN-gamma mRNA within 2 h post-stimulation. IL-2 was not detected in cell culture supernatants, but IL-2 receptor alpha chain (CD25) was detected in low density on a small proportion of T cells activated by C1q-bearing immune complexes. Secretion of both cytokines was inhibited partially, but not completely, by IL-10. These experiments show that immune complexes, potent inflammatory mediators, may activate T cells through a novel mechanism. These findings have implications for chronic inflammatory diseases in humans.
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PMID:T cell activation by soluble C1q-bearing immune complexes: implications for the pathogenesis of rheumatoid arthritis. 1251 87

Clinical data from 488 cats (1979-2000) with histopathologically confirmed feline infectious peritonitis (FIP) and 620 comparable controls were evaluated retrospectively to assess the value of several diagnostic tests frequently used in the evaluation of cats with suspected FIP. Diagnostic utility of serum albumin to globulin ratio for the diagnosis of FIP was greater than of the utility of serum total protein and gamma-globulin concentrations. Diagnostic utility of these variables was higher when performed on effusion. On effusion, positive and negative predictive values of Rivalta's test, a test that distinguishes between exudates and transudates (0.86 and 0.97), anti-coronavirus antibody detection (0.90 and 0.79), and immunofluorescence staining of coronavirus antigen in macrophages (1.00 and 0.57) were investigated. The positive and negative predictive values of presence of anti-coronavirus antibodies were 0.44 and 0.90, respectively, antibody concentrations (1:1,600) were 0.94 and 0.88. presence of immune complexes measured by a competitive enzyme-linked immunosorbent assay were 0.67 and 0.84, and detection of viral RNA by serum reverse-transcriptase polymerase chain reaction (RT-PCR) were 0.90 and 0.47. Effusion RT-PCR was performed in 6 cats; it was positive in all 5 cats with FIP and negative in the cat with another disease. Diagnostic assays on the fluid in cats with body effusion had good predictive values. Definitive diagnosis of FIP on the basis of measurement of various variables in serum was not possible. Serum tests can only be used to facilitate the decision for more invasive diagnostic methods.
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PMID:Comparison of different tests to diagnose feline infectious peritonitis. 1595 39

The aim of the current study was to confirm that tenascin-C large splice variant (TNC320) stimulates matrix metalloproteinase-1 (MMP-1) expression and to elucidate molecular mechanisms underlying this activation. The analysis of gene expression in cultured cells grown under different conditions indicated significant increases of MMP-1 mRNA steady-state levels in the cells treated with TNC320 (200%) compared with TNC220 (100%) and bovine serum albumin (BSA), which served as controls. Gel electrophoresis results demonstrated augmented MMP-1 protein in cells cultured with TNC320, whereas slight up-regulation was noticed in cells treated with TNC220 or fibronectin. Reverse transcriptase polymerase chain reaction results demonstrated significantly higher levels of MMP-1 gene expression in TNC320 cultured cells than in all other treatment groups. The result was confirmed by examining the level of MMP-1 promoter transactivation by different extracellular proteins. Data demonstrated 30-fold activation of MMP-1 promoter by TNC320 treatment in comparison with other treatments (TNC220 or fibronectin) and BSA as a control. Both invasion and collagenase activity assays demonstrated a 3-fold difference in the cells treated with TNC320 in comparison with the control. MMP-1 was quantified by enzyme-linked immunosorbent assay as well. Experiments with constitutively active expression kinases indicated that MMP-1 expression induced by TNC320 was associated with mitogen-activated protein kinase (MAPK) cascade activation. Culture with TNC320 resulted in more than 2-fold activation of MMP1-luciferase in the presence of mitogen-activated protein kinase kinase kinase 1 and also 2-fold down-regulation in the presence of mitogen-activated protein kinase kinase 1. We hypothesize that tenascin-C stimulates invasion via up-regulation of MMP-1 expression through activation of MAPK cascade signaling.
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PMID:Molecular mechanism of tenascin-C action on matrix metalloproteinase-1 invasive potential. 1739 87


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