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:1.11.1.7 (peroxidase)
65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The fate of tetanus toxin (mol wt 150,000) subsequent to its retrograde axonal transport in peripheral sympathetic neurons of the rat was studied by both electron microscope autoradiography and cytochemistry using toxin-horseradish peroxidase (HRP) coupling products, and compared to that of nerve growth factor (NGF), cholera toxin, and the lectins wheat germ agglutinin (WGA), phytohaemagglutinin (PHA), and ricin. All these macromolecules are taken up by adrenergic nerve terminals and transported retrogradely in a selective, highly efficient manner. This selective uptake and transport is a consequence of the binding of these macromolecules to specific receptive sites on the nerve terminal membrane. All these ligands are transported in the axons within smooth vesicles, cisternae, and tubules. In the cell bodies these membrane compartments fuse and most of the transported macromolecules are finally incorporated into lysosomes. The cell nuclei, the parallel golgi cisternae, and the extracellular space always remain unlabeled. In case the tetanus toxin, however, a substantial fraction of the labeled material appears in presynaptic cholinergic nerve terminals which innervate the labeled ganglion cells. In these terminals tetanus toxin-HRP is localized in 500-1,000 A diam vesicles. In contrast, such a retrograde transsynaptic transfer is not at all or only very rarely detectable after retrograde transport of cholera toxin, NGF, WGA, PHA, or ricin. An atoxic fragment of the tetanus toxin, which contains the ganglioside-binding site, behaves like intact toxin. With all these macromolecules, the extracellular space and the glial cells in the ganglion remain unlabeled. We conclude that the selectivity of this transsynaptic transfer of tetanus toxin is due to a selective release of the toxin from the postsynaptic dendrites. This release is immediately followed by an uptake into the presynaptic terminals.
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PMID:Selective retrograde transsynaptic transfer of a protein, tetanus toxin, subsequent to its retrograde axonal transport. 9 75

Conjugates of horseradish peroxidase with the lectins ricin (d-galactose), wheat germ agglutinin (N-acetylglucosamine), phytohemagglutinin (N-acetylgalactosamine), and with cholera toxin (GM1 ganglioside) were used for a cytochemical detection of corresponding termin al carbohydrates, or glycolipids on cell surfaces of cultured neurons and neuroblastoma cells. Cells were labeled at 4 degrees C with the above ligands and their adsorptive endocytosis was studied after incubations at 37 degrees C in a medium free of ligand. Peroxidase was detected by the method of Graham and Karnovsky (J. Histochem. Cytochem. 14:291, 1966). Lectins and cholera toxin underwent endocytosis in cisternae and vesicles of GERL (Golgi-Endoplasmic Reticulum-Lysosome). We suggest that GERL is the primary ercipieint of adsorptively endocytosed plasma membrane "receptor"-ligand complexes which are thus degraded or possibly reutilized (recycling). Wheat germ agglutinin-horseradish peroxidase conjugates used in vivo for studies of retrograde axonal transport were significantly more sensitive than free horseradish peroxidase.
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PMID:The use of lectins and cholera toxin for the detection of surface carbohydrates of cultured neurons and neuroblastoma. 47 60

The uptake of macromolecules by nerve terminals which is followed by retrograde axonal transport seems to occur by two different mechanisms, a specific and a nonspecific one. The nonspecific uptake depends on the presence of macromolecules (e.g., horseradish peroxidase) in the vicinity of the nerve terminals at very high concentrations and is enhanced by neuronal activity. In contrast, the specific uptake and subsequent retrograde axonal transport becomes apparent at much lower concentrations of the appropriate macromolecules, depends on the affinity of these ligands for specific binding sites on the surface of the neuronal membrane, and is independent of neuronal activity. The fact that lectins and some bacterial toxins bind to specific membrane glycoproteins or glycolipids allows conclusions to be drawn regarding qualitative and even quantitative aspects of the composition of the plasma membrane of the nerve terminals. 125I-labelled nerve growth factor (NGF), tetanus toxin, cholera toxin, wheat germ agglutinin (WGA), ricin II, phytohemagglutinin (PHA), and concanavalin A (ConA) were injected into the anterior eye chamber of rats where they were taken up by adrenergic nerve terminals and transported retrogradely to the superior cervical ganglion. The saturation of the uptake-transport found for NGF, WGA, choleragenoid and an atoxic binding-fragment of tetanus toxin indicates that limited numbers of binding sites, which showed also different affinities, are present for each ligand on the membrane of the nerve terminals. Competition experiments showed that the binding sites for the ligands investigated are largely independent. Two different classes of binding sites (high affinity--low capacity and intermediate affinity--intermediate capacity) seem to be involved in the saturable retrograde axonal transport of NGF. In contrast, WGA seems to have only a single class of binding-uptake sites with high capacity and relatively low affinity. Strong evidence for positive cooperativity was obtained for the uptake and subsequent transport of the tetanus toxin fragment.
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PMID:Retrograde axonal transport of specific macromolecules as a tool for characterizing nerve terminal membranes. 51 57

Ricin-resistant (RicR) baby hamster kidney (BHK) cell lines have been classified into a small group (3 lines) showing a minimal surface change from wild type and a larger group (20 lines) which exhibit more extreme alterations in surface properties. Glycopeptides released by pronase from some RicR lines in the second group show a lower content of sialic acid, galactose, and N-acetylglucosamine and greatly reduced binding activity for ricin. Treatment of receptor deficient glycopeptides or RicR cells with neuraminidase reveals new ricin receptors and renders the cells very sensitive to ricin. Several classes of ricin receptors are postulated for BHK cells, some of which are cryptic and under independent genetic control from receptors selected against with ricin. The cell lines showing greatly altered surface properties in general adhere poorly to a substratum and also aggregate poorly compared to wild type or RicR cells showing minimal surface change. The lactoperoxidase iodinateable 250K glycoprotein of normal BHK cells is lacking in all but one of these RicR cell lines. The role of 250K glycoprotein in normal cell adhesion is considered and a hypothesis proposed relating changes in surface organization of the 250K glycoprotein to alterations in receptors induced by ricin selection.
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PMID:Lectin receptors and cell surface recognition. 66 23

Ricin A chain was radioactively labeled using reductive alkylation, lactoperoxidase catalyzed iodination, and reaction with iodoacetamide or N-ethylmaleimide (NEM). The inhibition of cell-free rat liver protein synthesis by the modified A chains and the ribosome binding characteristics of each of the labeled derivatives was examined. [3H] NEW was found to quantitatively react with the A chain sulfhydryl group normally involved in a disulfide bond with the B chain in intact ricin. Labeling the protein with [3H] NEM had no effect on the in vitro inhibition of protein synthesis by the A chain. [3H] NEM-labeled A chain binds to rat liver ribosomes in a manner which is dependent on the concentrations of NaCl and Mg2+. At optimal Mg2+ concentration (5.5 mM), A chain binding to ribosomes is saturable and fully reversible either by dilution of the reaction mixture or by addition of unlabeled A chain. At 5.5 mM Mg2+, A chain was found to bind to a single site on rat liver ribosomes with a dissociation constant of 6.2 x 10(-8) M. [3H] NEM-labeled A chain did not bind to isolated 40S ribosomal subunits and bound to 60S ribosomal subunits with a 1 : 1 molar stoichiometry and a dissociation constant of 2.2 x 10(-7) M. The relationship between ribosome binding and A chain inhibition of eucaryotic protein synthesis is discussed.
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PMID:Binding of ricin A chain to rat liver ribosomes: relationship to ribosome inactivation. 74 77

The surface glycoproteins of baby hamster kidney (BHK) cells were iodinated by lactoperoxidase and submitted to a two-dimensional electrophoresis procedure involving isoelectric focusing in the first dimension and SDS gel electrophoresis in the second dimension. After autoradiography a complex but reproducible pattern was obtained. The technique was then applied to the study of three ricin-resistant mutant clones with reduced rates of cell-cell and/or cell-substratum adhesion. Abnormal patterns were observed in all three mutant clones indicating different mechanisms of ricin resistance and identifying glycoproteins which may be involved in cellular interactions.
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PMID:Two-dimensional electrophoresis of surface glycoproteins of normal BHK cells and ricin resistant mutants. 76 Jul 85

1. Growth of baby hamster kidney (BHK) cells in medium containing 2-deoxy-D-glucose is retarded in direct proportion of the 2-deoxyglucose concentration. The severity of the effect is reduced in medium containing high relative concentrations of glucose. 2. 2-Deoxyglucose inhibits the incorporation of radioactivity from mannose, galactose, glucosamine, fucose and N-acetylmannosamine precursors into acid-insoluble cellular material. Incorporation of radioactively labelled leucine into protein is not affected by 2-deoxyglucose. 3. BHK cells grown in the presence of 2-deoxyglucose become less sensitive to the toxic action of certain plant lectins, ricin of Ricinus communis and Phaseolus vulgaris phytohaemagglutinin, which bind specifically to cell surface galactose and N-acetyl-galactosamine residues. By contrast, 2-deoxyglucose increased the sensitivity of BHK cells to the weak toxicity of concanavalin A, which binds to surface mannosides. Treated cells also become more agglutinable with concanavalin A. 4. Cell surface glycoprotein labelled by lactoperoxidase-catalysed iodination have been examined by dodecylsulphate-polyacrylamide gel electrophoresis. The radio-iodinated glycoprotein prepared from cells grown in medium containing 2-deoxyglucose migrate more rapidly than glycoproteins from cells grown in the absence of inhibitor.
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PMID:Effect of 2-deoxy-D-glucose on the cell-surface glycoproteins of hamster fibroblasts,. 83 18

A variant of the murine lymphoma cell line BW5147 that was 250 times more resistant than the parent to Ricinus communis II agglutinin (RCAII, ricin) toxicity (measured in the absence of serum) was selected by repeated exposure of cells to increasing concentrations of the lectin. Quantitative binding of the lectin, however, was decreased by only 30-40% in the variant. In contrast with several reported lectin-resistant variants, most surface glycoproteins on the parental and variant cell surfaces were similar, as judged by electrophoresis after lactoperoxidase-catalyzed iodination and RCAI-affinity chromatography. Surface studies showed that an RCAI- and RCAII-binding protein of about 80,000 daltons on the surfaces of parental cells is altered on the variant cells to a form with a lower apparent molecular weight. We suggested that this protein is important for entry of RCAII molecules in parental cells, but that its altered form on the variant cells no longer mediates efficient RCAII uptake, thus imparting toxin resistance. In addition, a protein of approximately 35,000 daltons, which does not bind RCAI, is weakly lactoperoxidase-iodinated on parental but not variant cells.
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PMID:Cell-surface changes in Ricinus communis toxin (ricin)-resistant variant of a murine lymphoma. 84 78

Conjugates of ricin agglutinin and phytohemagglutinin with horseradish peroxidase (HRP) were used for a cytochemical study of internalization of their plasma membrane "receptors" in cultured isolated mouse dorsal root ganglion neurons. Labeling of cells with lectin-HRP was done at 4 degrees C, and internalization was performed at 37 degrees C in a culture medium free of lectin-HRP. 15-20 min after incubation at 37 degrees C, lectin-HRP receptor complexes were seen in vesicles or tubules located near the plasma membrane. After 1-3 h at 37 degrees C, lectin-HRP-receptor complexes accumulated in vesicles and tubules corresponding to acid phosphatase-rich vesicles and tubules (GERL) at the trans aspect of the Golgi apparatus. A few coated vesicles and probably some dense bodies contained HRP after 3-6 h of incubation at 37 degrees C. Soluble HRP was not endocytosed under the conditions of this experiment or when it was present in the incubation medium at 37 degrees C. Internalization of lectin-HRP-receptor conjugates was decreased or inhibited by mitochondrial respiration inhibitors but not by cytochalasin B or colchicine. These studies indicate that lectin-labeled plasma membrane moieties of neurons are endocytosed primarily in elements of GERL.
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PMID:Internalization of lectins in neuronal GERL. 85 27

The binding, mobility, and mode of cell entry of the plant toxin ricin (or RCAII) were investigated on susceptible and partially resistant murine cell lines. When susceptible cells (SV40-transformed 3T3 fibroblast cells and BW5147 lymphoma cells) were examined, ricin bound rapidly, induced endocytosis, and entered the cell cytoplasm via broken endocytotic vesicles to inhibit cell protein synthesis, as found previously (1). Addition of lactose within 15 min after initial ricin binding prevented toxicity. After this time lactose addition no longer blocked the inhibition of protein synthesis. In a partially resistant lymphoma (BW5147/RCA3) that shows only a slight reduction in the total number of ricin-binding sites, ricin bound rapidly to the cell surface, but was endocytosed significantly less at low ricin doses compared to its parental line, indicating a possible difference in cell surface behavior. The exposed surface proteins on the BW5147 parental and BW5147/RCA3 resistnat lines were examined by 125I-labeling utilizing lactoperoxidase-catalyzed iodination. The radiolabeled components were solubilized and separated by slab electrophoresis in sodium dodecyl sulfate. Autoradiograms of the slab gels indicated that two surface components of approximately 80,000 and 35,000 mol wt were much less exposed or were missing on the resistant line.
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PMID:Cell surface receptors and their dynamics on toxin-treated malignant cells. 125 60


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