Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.11.1.7 (peroxidase)
 65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cultured rat embryo fibroblasts were first allowed to store for 24 h fluorescein-labeled goat immunoglobulins directed against rabbit immunoglobulins (F anti-R IgG), and were subsequently exposed for 24 h to [(3)H]acetylated rabbit immunoglobulins known to bind to the cell membrane either specifically (anti-plasma membrane IgG: A anti-PM IgG) or unspecifically (contol IgG: AC IgG). As a result of immunological interaction between the two antibodies (no effect was found if the cells had been preloaded with control goat FC IgG), a substantial portion of the stored F anti-R IgG was unloaded from its intracellular storage site, appearing in the medium in the form of soluble immune complexes with rabbit A IgG. Part of the unloaded F anti-R IgG also was recovered in association with the plasma membrane, but only when A anti-PM IgG was used. In addition, significant reverse translocation of AC IgG from plasma membrane to lysosomes or some related intracellular storage compartment was also observed. With A anti-PM IgG, this translocation was less marked and affecte at the same time the plasma membrane marker 5'- nucleotidase. Cells that had stored horseradish peroxidase (HRP) simultaneously with F anti-R IgG did not unload HRP when exposed to A anti-PM IgG. These results support strongly, though not unequivocally, the concept that plasma membrane patches interiorized by endocytosis are recycled, or shuttled, back to the cell surface. In the framework of this concept, recycling antibody-coated membrane is taken to serve as vehicle for the selective intracellular capture and extracellular discharge of immunologically bound F anti-R IgG. The alternative explanation of regurgitation triggered off by immune complexes is considered less likely in view of the lack of HRP unloading.
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PMID:Fate of plasma membrane during endocytosis. II. Evidence for recycling (shuttle) of plasma membrane constituents. 47 10

The endodermal trophotaenial epithelium in goodeid embryos acts as a placental exchange site. Fine structural and cytochemical data indicate that the trophotaenial absorptive cells are endocytotically highly active. To test their micropinocytotic capacity and characterize the cellular mechanisms involved in membrane, solute and ligand movements, living embryos of Xenoophorus captivus were incubated in saline media containing horseradish peroxidase (HRP) and/or cationized ferritin (CF) in vitro, and the uptake of these tracer proteins examined by both time sequence analysis and pulse-chase procedures. In some embryos, the effects of prolonged exposure to CF injected into the ovarian cavity, was also investigated. Labelling of the free cell surface was detectable with CF only, but interiorization of both probes was quick from all incubation media. Adsorptive pinocytosis of CF and fluid-phase uptake of HRP sequentially labelled pinocytic vesicles, endosomes, and lysosome-like bodies. In addition, CF-molecules were sequestered within apical tubules and small vesicles. HRP was largely excluded from both organelles and ended up in the lysosomal compartment. For CF, two alternative pathways were indicated by the pulse-chase experiments; transcellular passage and regurgitation of tracer molecules to the apical cell surface. The latter procedure involves membrane and receptor recycling, in which apical tubules are thought to mediate. In double-tracer experiments, using an 8:1 excess of HRP, external labelling with CF was light or lacking after 1-3 min, and the initial uptake-phase produced pinocytic vesicles and endosomes that mainly contained HRP-reaction product. Prolonged incubation, however, resulted in densely CF-labelled plasmalemmal invaginations and pinocytic vesicles that predominantly carried ferritin granules. After 60 min, the vacuoles of the endosomal compartment contained either high concentrations of HRP-reaction product, both tracers side by side, or virtually exclusively CF.
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PMID:Maternal-embryonic relationships in the goodeid teleost, Xenoophorus captivus. The vacuolar apparatus in trophotaenial absorptive cells and its role in macromolecular transport. 341 34

The vesicular transport system for biliary secretion of plasma-derived proteins was investigated in rats with chronic bile duct obstruction. Horseradish peroxidase, previously demonstrated to be a suitable tracer for vesicular transport, was employed in these studies. Both the time course of horseradish peroxidase secretion into bile and the morphological events in its uptake, transport, and biliary secretion were found to proceed in a manner essentially identical to that of sham-operated control animals. In addition, fragmentation of hepatocytes leading to sloughing into bile of large pieces of cytoplasm bearing horseradish peroxidase-containing endocytic transport vesicles frequently was observed in the cholestatic animals. These data suggest that the vesicular transport system for the secretion into bile of plasma-derived proteins remains intact and functional during chronic bile duct obstruction and that another mechanism, possibly fragmentation and solubilization of hepatocyte membranes followed by regurgitation of proteins released from endocytic vesicles, may be responsible for the elevation of biliary proteins within plasma seen during cholestasis.
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PMID:Vesicular transport of horseradish peroxidase during chronic bile duct obstruction in the rat. 661 34

We have compared the effects of three perturbations (treatment with 2 microM monensin, potassium depletion, and incubation in 0.35 M NaCl) on recycling of internalized fluid-phase, bulk-membrane, and receptor-mediated tracers in rat fetal fibroblasts. Monensin accelerated 2-fold the regurgitation of the fluid-phase tracer horseradish peroxidase (HRP), as previously described in these cells after potassium depletion or upon incubation in hypertonic medium (1), and all treatments severely inhibited transfer of HRP from endosomes to lysosomes. In comparison, recycling of (6-[N-(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]hexanoyl glucosylsphingosine (C6-NBD-GlcCer), a fluorescent lipid used as a bulk-membrane probe, was not significantly affected while transferrin recycling was slowed down 2-fold. The striking similarities of these unrelated perturbations in their distinct effects on fluid, bulk-membrane, and receptor addressing point to common targets regulating these mechanisms.
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PMID:Three unrelated perturbations similarly uncouple fluid, bulk-membrane, and receptor endosomal flow in rat fetal fibroblasts. 924 9

Stable transformation of Rat-1 fibroblasts by the v-Src oncoprotein results into the constitutive formation of macropinosomes. In the present report, we found that macropinosomes do not fuse with transferrin-containing endosomes and investigated the effects of cyclic AMP as a regulator of macropinocytosis in this cell system. The permeant analogs dibutyryl cyclic AMP and 8-bromo-cyclic AMP, as well as the pharmacological activator of adenylate cyclase forskolin, similarly decreased by about 35% the net endocytic accumulation of the fluid-phase tracer horseradish peroxidase at intervals >5 minutes in v-Src-transformed cells but not in the non-transformed parental Rat-1 cell line. However, and in contrast to the phospholipase C inhibitor 2-nitro-4-carboxyphenyl-N, N-diphenylcarbamate or the phosphatidylinositol 3-kinase inhibitor wortmannin, dibutyryl cyclic AMP neither returned the peroxidase accumulation rate of v-Src-transformed cells to that of parental Rat-1/control cells, nor prevented macropinosome formation, as shown by confocal microscopy. Detailed analysis of the kinetics of tracer entry and efflux in transformed cells revealed that dibutyryl cyclic AMP inhibited peroxidase accumulation only after intervals >5 minutes, due to accelerated peroxidase regurgitation, but did not alter the rate of transferrin recycling. Taken together, these data indicate that, in v-Src-transformed fibroblasts, macropinocytosis and micropinocytosis serve different pathways and that cyclic AMP affects neither micropinocytosis nor the formation of macropinosomes, but selectively promotes regurgitation therefrom.
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PMID:Regulation of macropinocytosis in v-Src-transformed fibroblasts: cyclic AMP selectively promotes regurgitation of macropinosomes. 968 28

The dicationic macrolide antibiotic azithromycin inhibits the uptake of horseradish peroxidase (HRP) by fluid-phase pinocytosis in fibroblasts in a time- and concentration-dependent fashion without affecting its decay (regurgitation and/or degradation). The azithromycin effect is additive to that of nocodazole, known to impair endocytic uptake and transport of solutes along the endocytic pathway. Cytochemistry (light and electron microscopy) shows a major reduction by azithromycin in the number of HRP-labeled endocytic vesicles at 5 min (endosomes) and 2 h (lysosomes). Within 3 h of exposure, azithromycin also causes the appearance of large and light-lucentlelectron-lucent vacuoles, most of which can be labeled by lucifer yellow when this tracer is added to culture prior to azithromycin exposure. Three days of treatment with azithromycin result in the accumulation of very large vesicles filled with pleiomorphic content, consistent with phospholipidosis. These vesicles are accessible to fluorescein-labeled bovine serum albumin (FITC-BSA) and intensively stained with filipin, indicating a mixed storage with cholesterol. The impairment of HRP pinocytosis directly correlates with the amount of azithromycin accumulated by the cells, but not with the phospholipidosis induced by the drug. The proton ionophore monensin, which completely suppresses azithromycin accumulation, also prevents inhibition of HRP uptake. Erythromycylamine, another dicationic macrolide, also inhibits HRP pinocytosis in direct correlation with its cellular accumulation and is as potent as azithromycin at equimolar cellular concentrations. We suggest that dicationic macrolides inhibit fluid-phase pinocytosis by impairing the formation of pinocytic vacuoles and endosomes.
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PMID:Azithromycin, a lysosomotropic antibiotic, impairs fluid-phase pinocytosis in cultured fibroblasts. 1149 89