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:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We determined the expression levels of the mdr1 and mdr3 multidrug-resistance genes (also known as PGY1 and PGY3, respectively) in peripheral blood cells from 69 adult patients with acute and chronic leukemias, using an RNase protection assay. Expression of mdr1 was found in samples from patients with acute nonlymphocytic leukemia (13 of 17), chronic myelocytic leukemia (CML, chronic phase, 10 of 10; blast crisis, three of four), acute lymphocytic leukemia (ALL, eight of 11), B-cell chronic lymphocytic leukemia (B-CLL, 17 of 17), hairy cell leukemia (HCL, one of two), and T-cell prolymphocytic leukemia (one of one), but not in B-cell prolymphocytic leukemia (B-PLL, 0 of seven). Expression of mdr3 was only detected in samples from B-cell lymphocytic leukemias: CML, lymphoid blast crisis (one of one), B-cell ALL (two of two), B-CLL (17 of 17), B-PLL (seven of seven), and HCL (two of two). In vitro drug uptake studies by on-line flow cytometry showed that in leukemia cells expressing either mdr1 or mdr3, the steady-state accumulation of daunorubicin could be significantly increased by addition of cyclosporine and, to a lesser extent, by verapamil. Because cyclosporine and verapamil are known as inhibitors of the mdr1-encoded P-glycoprotein drug-efflux pump, and because the mdr1 and mdr3 genes are highly homologous, our data suggest that the mdr3 gene encodes a functional drug pump in B-cell lymphocytic leukemias. The results of this study may have implications for clinical therapy for acute or chronic leukemias expressing the mdr1 or mdr3 gene, in particular, treatment with combinations of cytotoxic drugs plus agents that reverse multidrug resistance. Since mdr1 and mdr3 are frequently expressed in untreated as well as treated leukemia, such combination therapy should be considered for untreated patients as well as treated patients.
...
PMID:Expression of mdr1 and mdr3 multidrug-resistance genes in human acute and chronic leukemias and association with stimulation of drug accumulation by cyclosporine. 197 61

We have previously demonstrated the presence of a reverse transcriptase-like enzyme in retroviral particles from patients with essential thrombocythemia, polycythemia vera, and chronic myelogenous leukemia. It was subsequently shown that the human genome contains 50 copies of HERV-K. HERV-K is a human endogenous class I retroviral element that contains gag, pol, and env open reading frames. Using both reverse transcriptase-polymerase chain reaction and ribonuclease protection assays, it is demonstrated that the HERV-K pol is expressed in human blood leukocytes. The data indicates that this expression is restricted in CML white cells and is the result of gene regulation.
...
PMID:Expression of human endogenous retrovirus (HERV-K) in chronic myeloid leukemia. 750 41

Normal expression of the hematopoietic growth factor receptor FLT3 (STK-1@Flk2) is limited to CD34+ stem/progenitor cells. We have evaluated the expression of FLT3 by RNase protection assay and Western blotting in 161 primary bone marrow (BM) samples from patients with leukemia. FLT3 RNA was found to be expressed at a higher level than in normal BM controls in 33 of 33 B-lineage acute leukemias, 11 of 12 acute myeloid leukemias (AMLs), and 3 of 11 T-cell acute leukemias (T-ALLs). Expression of FLT3 RNA was also observed in some cases of blast crisis CML. The FLT3 signal resulted from expression on the leukemic blasts, and was not caused by increased FLT3 expression on normal CD34+ stem/progenitor cells in the leukemic samples. To determine if FLT3 protein was also overexpressed, proteins were extracted from leukemic BM samples and screened by Western blotting with anti-FLT3 antisera. FLT3 protein was not detected in normal BM controls, but was found in 14 of 14 B-lineage ALLs, 36 of 41 AMLs, and 1 of 4 T-ALLs. Stimulation of patient samples with FLT3 ligand resulted in autophosphorylation of the FLT3 receptor, suggesting the receptor is functional in these cells. These data show that FLT3 RNA and protein are aberrantly expressed by AML and ALL cells in that CD34 expression and FLT3 expression are no longer synchronous, and suggest the possibility that overexpression of FLT3 could play a role in the survival and/or proliferation of malignant clones in acute myeloid and lymphoid leukemias.
...
PMID:Expression of the hematopoietic growth factor receptor FLT3 (STK-1/Flk2) in human leukemias. 856 34

Nepsilon-(Carboxymethyl)lysine (CML) is an advanced glycation end product formed on protein by combined nonenzymatic glycation and oxidation (glycoxidation) reactions. We now report that CML is also formed during metal-catalyzed oxidation of polyunsaturated fatty acids in the presence of protein. During copper-catalyzed oxidation in vitro, the CML content of low density lipoprotein increased in concert with conjugated dienes but was independent of the presence of the Amadori compound, fructoselysine, on the protein. CML was also formed in a time-dependent manner in RNase incubated under aerobic conditions in phosphate buffer containing arachidonate or linoleate; only trace amounts of CML were formed from oleate. After 6 days of incubation the yield of CML in RNase from arachidonate was approximately 0.7 mmol/mol lysine compared with only 0.03 mmol/mol lysine for protein incubated under the same conditions with glucose. Glyoxal, a known precursor of CML, was also formed during incubation of RNase with arachidonate. These results suggest that lipid peroxidation, as well as glycoxidation, may be an important source of CML in tissue proteins in vivo and that CML may be a general marker of oxidative stress and long term damage to protein in aging, atherosclerosis, and diabetes.
...
PMID:The advanced glycation end product, Nepsilon-(carboxymethyl)lysine, is a product of both lipid peroxidation and glycoxidation reactions. 862 37

Advanced glycation end-products and glycoxidation products, such as Nepsilon-(carboxymethyl)lysine (CML) and pentosidine, accumulate in long-lived tissue proteins with age and are implicated in the aging of tissue proteins and in the development of pathology in diabetes, atherosclerosis and other diseases. In this paper we describe a new advanced glycation end-product, Nepsilon-(carboxyethyl)lysine (CEL), which is formed during the reaction of methylglyoxal with lysine residues in model compounds and in the proteins RNase and collagen. CEL was also detected in human lens proteins at a concentration similar to that of CML, and increased with age in parallel with the concentration of CML. Although CEL was formed in highest yields during the reaction of methylglyoxal and triose phosphates with lysine and protein, it was also formed in reactions of pentoses, ascorbate and other sugars with lysine and RNase. We propose that levels of CML and CEL and their ratio to one another in tissue proteins and in urine will provide an index of glyoxal and methylglyoxal concentrations in tissues, alterations in glutathione homoeostasis and dicarbonyl metabolism in disease, and sources of advanced glycation end-products in tissue proteins in aging and disease.
...
PMID:N-epsilon-(carboxyethyl)lysine, a product of the chemical modification of proteins by methylglyoxal, increases with age in human lens proteins. 918 19

Glycation is a non-enzymatic posttranslational modification that involves a covalent linkage between a sugar and an amino group of protein molecule forming ketoamine. Subsequent oxidation, fragmentation and/or crosslinking of ketoamine leads to the production of advanced glycation endproducts (AGEs). Formation of AGEs causes detrimental effects on the structure and function of affected proteins. Accumulation of AGEs has been implicated in normal aging and in the pathogenesis of diabetes-associated complications and Alzheimer's disease (AD). Of all AGEs, Nepsilon-(carboxymethyl)lysine (CML) is a major glycoxidation product known to be stable and accumulate progressively in vivo. In order to determine if tau is glycated in AD, we raised a rabbit antibody to CML that demonstrated its usefulness in detecting glycation of different proteins in vitro, including BSA, ribonuclease, lysozyme and recombinant tau. Immunochemical analyses indicated that ribose and glucose-6-phosphate are more effective than glucose in generating CML formation in these proteins. We used this antibody to probe for glycation in the following human tau preparations: tau of normal brains and preparations of soluble PHF-tau as well as insoluble PHF from AD brains. All three principal tau components resolved from PHF-tau on Western blots showed CML immunoreactivity indicating that tau is glycated in PHF-tau; and insoluble PHF exhibited prominent CML immunoreactivity on top of the stacking gel. Moreover, immunoelectron microscopic analyses indicate that the anti-CML antibody labels predominantly PHF in aggregates. Taken together, these results suggest that tau becomes glycated in PHF-tau and glycation may play a role in stabilizing PHF aggregation leading to tangle formation in AD.
...
PMID:An immunochemical study on tau glycation in paired helical filaments. 1036 87

Reactive aldehydes derived from reducing sugars and peroxidation of lipids covalently modify proteins and may contribute to oxidative tissue damage. We recently described another mechanism for generating reactive aldehydes from free alpha-amino acids. The pathway begins with myeloperoxidase, a heme enzyme secreted by activated neutrophils. Conversion of alpha-amino acids to aldehydes requires hypochlorous acid (HOCl), formed from H2O2 and chloride by myeloperoxidase. When L-serine is the substrate, HOCl generates high yields of glycolaldehyde. We now demonstrate that a model protein, ribonuclease A (RNase A), exposed to free L-serine and HOCl exhibits the biochemical hallmarks of advanced glycation end (AGE) products -- browning, increased fluorescence, and cross-linking. Furthermore, Nepsilon-(carboxymethyl)lysine (CML), a chemically well-characterized AGE product, was generated on RNase A when it was exposed to reagent HOCl-serine, the myeloperoxidase-H2O2-chloride system plus L-serine, or activated human neutrophils plus L-serine. CML production by neutrophils was inhibited by the H2O2 scavenger catalase and the heme poison azide, implicating myeloperoxidase in the cell-mediated reaction. CML was also generated on RNase A by a myeloperoxidase-dependent pathway when neutrophils were activated in a mixture of amino acids. Under these conditions, we observed both L-serine-dependent and L-serine-independent pathways of CML formation. The in vivo production of glycolaldehyde and other reactive aldehydes by myeloperoxidase may thus play an important pathogenic role by generating AGE products and damaging tissues at sites of inflammation.
...
PMID:The myeloperoxidase system of human phagocytes generates Nepsilon-(carboxymethyl)lysine on proteins: a mechanism for producing advanced glycation end products at sites of inflammation. 1039 4

Advanced glycation end products (AGEs) derived from glucose are implicated in the pathogenesis of diabetic vascular disease. However, many lines of evidence suggest that other pathways also promote AGE formation. One potential mechanism involves oxidants produced by the NADPH oxidase of neutrophils, monocytes, and macrophages. In vitro studies have demonstrated that glycolaldehyde, a product of serine oxidation, reacts with proteins to form N(epsilon)-(carboxymethyl)lysine (CML), a chemically well-characterized AGE. We used mice deficient in phagocyte NADPH oxidase (gp91-phox(-/-)) to explore the role of oxidants in AGE production in isolated neutrophils and intact animals. Activated neutrophils harvested from wild-type mice generated CML on ribonuclease A (RNase A), a model protein, by a pathway that required L-serine. CML formation by gp91-phox(-/-) neutrophils was impaired, suggesting that oxidants produced by phagocyte NADPH oxidase contribute to the cellular formation of AGEs. To determine whether these observations are physiologically relevant, we used isotope-dilution gas chromatography/mass spectrometry to quantify levels of protein-bound CML in mice suffering from acute peritoneal inflammation. Phagocytes from the gp91-phox(-/-) mice contained much lower levels of CML than those from the wild-type mice. Therefore, oxidants generated by phagocyte NADPH oxidase may play a role in AGE formation in vivo by a glucose-independent pathway.
...
PMID:Production of N(epsilon)-(carboxymethyl)lysine is impaired in mice deficient in NADPH oxidase: a role for phagocyte-derived oxidants in the formation of advanced glycation end products during inflammation. 1288 33

Proteomic analysis using electrospray liquid chromatography-mass spectrometry (ESI-LC-MS) has been used to compare the sites of glycation (Amadori adduct formation) and carboxymethylation of RNase and to assess the role of the Amadori adduct in the formation of the advanced glycation end-product (AGE), N(epsilon)-(carboxymethyl)lysine (CML). RNase (13.7 mg/mL, 1 mM) was incubated with glucose (0.4 M) at 37 degrees C for 14 days in phosphate buffer (0.2 M, pH 7.4) under air. On the basis of ESI-LC-MS of tryptic peptides, the major sites of glycation of RNase were, in order, K41, K7, K1, and K37. Three of these, in order, K41, K7, and K37 were also the major sites of CML formation. In other experiments, RNase was incubated under anaerobic conditions (1 mM DTPA, N2 purged) to form Amadori-modified protein, which was then incubated under aerobic conditions to allow AGE formation. Again, the major sites of glycation were, in order, K41, K7, K1, and K37 and the major sites of carboxymethylation were K41, K7, and K37. RNase was also incubated with 1-5 mM glyoxal, substantially more than is formed by autoxidation of glucose under experimental conditions, but there was only trace modification of lysine residues, primarily at K41. We conclude the following: (1) that the primary route to formation of CML is by autoxidation of Amadori adducts on protein, rather than by glyoxal generated on autoxidation of glucose; and (2) that carboxymethylation, like glycation, is a site-specific modification of protein affected by neighboring amino acids and bound ligands, such as phosphate or phosphorylated compounds. Even when the overall extent of protein modification is low, localization of a high proportion of the modifications at a few reactive sites might have important implications for understanding losses in protein functionality in aging and diabetes and also for the design of AGE inhibitors.
...
PMID:Proteomic analysis of the site specificity of glycation and carboxymethylation of ribonuclease. 1458 47

Methylglyoxal (MG) is generated through the Embden-Meyerhof and polyol pathways, and it rapidly reacts with proteins to form advanced glycation end products (AGE) such as N(epsilon)-(carboxyethyl)lysine (CEL). In the present study, polyclonal and monoclonal antibodies specific for CEL were prepared to estimate CEL content in aldehydes-modified proteins and the pathological localization in human kidneys. Polyclonal CEL-specific antibody was prepared by removing cross-reactive antibodies against N(epsilon)-(carboxymethyl) lysine (CML), one of the major AGE structures, using CML-conjugated affinity chromatography. Monoclonal CEL-specific antibody (CEL-SP) was obtained by immunization with CEL-bovine serum albumin, followed by successive screening according to CEL-RNase-positive but CML-RNase-negative criteria. A non-competitive ELISA showed that both the polyclonal and monoclonal CEL-specific antibodies significantly reacted with CEL-proteins but not with CML-proteins. A competitive ELISA also demonstrated that CEL-SP does not show cross-reactivity against CEL analogues such as CML, carboxymethylarginine (CMA) and S-carboxymethylcysteine (CMC), thus indicating that antibody is able to recognize the difference of one methyl group between carboxymethyl group and carboxyethyl group. Furthermore, CEL-SP significantly reacted with human serum albumin modified with MG but not with glyoxal or 3-deoxyglucosone, and its reactivity was highly correlated with the CEL content, which was determined by high performance liquid chromatography. Immunohistochemical studies using CEL-SP provided evidence that CEL-modified proteins accumulate in distal tubular epithelial cells of the diabetic rat. These results demonstrate that a specific antibody against CEL can be a powerful tool for detecting CEL both in vitro and in vivo.
...
PMID:Immunochemical detection of Nepsilon-(carboxyethyl)lysine using a specific antibody. 1824 32


1

---