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Query: UNIPROT:P06889 (Mol)
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Specific binding of tritium-labeled platelet-activating factor (PAF) and a nonmetabolizable bioactive analog of PAF, 1-O-alkyl-2-N-methylcarbamyl-sn-glyceryl-3-phosphorylcholine, to human platelet membranes was found to be potentiated by wheat germ agglutinin (WGA) and erythroagglutinin. As demonstrated in Scatchard plots, the potentiation effect is due to an increase in the maximal number of receptor sites, with no alteration in the equilibrium dissociation constant. The WGA-potentiated specific binding can be specifically inhibited by N-acetylglucosamine, shows identical affinity for PAF agonists and a receptor antagonist, L-659,989, and has an identical Na+ inhibition pattern to non-treated membranes in the absence of WGA. The WGA-induced potentiation is preferential in the plasma membrane-enriched fraction. The maximal number of receptor sites increases in membranes pretreated with neuraminidase and beta-N-acetylglucosaminidase. Therefore, WGA may bind to an endogenous PAF receptor modulator, which then either dissociates from or associates with the PAF receptor and regulates the receptor conformation. The membrane fraction enriched with intracellular membranes is also enriched with PAF receptors. WGA was also found to increase the maximal aggregation of rabbit and human platelets induced by PAF and to induce the synthesis of PAF, which preceded aggregation in human platelets. An intracellular PAF receptor may also exist, and it could modulate the function of PAF retained inside of the stimulated cells.
Mol Pharmacol 1991 Jun
PMID:Wheat germ agglutinin potentiates specific binding of platelet-activating factor to human platelet membranes and induces platelet-activating factor synthesis in intact platelets. 205 92

The size of a lysosomal cysteine proteinase from epimastigotes of Trypanosoma cruzi decreased from 60 to 54 kDa upon treatment with endo beta-N-acetylglucosaminidase H. A lower-molecular weight component (30-35 kDa), which usually accompanies the 60-kDa protein also increased its electrophoretic mobility, and seems to consist of a mixture of degradation products of the enzyme, since both the larger and the smaller components had the same N-terminal sequence as the 60-kDa protein. The amino acid composition of the protein moiety and the composition of the oligosaccharide chains have been determined. The oligosaccharide chains are of the high-mannose type, and contain 6, 7, 8 or 9 mannose residues, as shown both by in vivo labeling with [U-14C]glucose, and by labeling the endo-beta-N-acetylglucosaminidase H-sensitive oligosaccharides of the purified enzyme with tritiated sodium borohydride. The oligosaccharide chains did not contain phosphate residues. Further studies with [U-14C]-labeled total glycoproteins of T. cruzi and enzyme assays, suggest that T. cruzi and other trypanosomatids do not target their lysosomal enzymes to the organelle through the mannose-6-phosphate marker pathway.
Mol Biochem Parasitol 1990 Jan 01
PMID:Amino acid and carbohydrate composition of a lysosomal cysteine proteinase from Trypanosoma cruzi. Absence of phosphorylated mannose residues. 218 4

Chicken heterophile antigenic determinant (CHAD-1) has been previously found in medullary lymphocytes of the bursa and thymus as well as in some non-lymphoid cells by the immunoperoxidase method, using rabbit antiserum to a complete Freund's adjuvant (CFA) as the first antibody. In this work we demonstrated that absorption of anti-CFA serum with highly purified preparations of hen egg white glycoproteins (ovomucoid, ovoinhibitor, ovalbumin) or chicken orosomucoid completely blocked immunoperoxidase staining for CHAD-1. Treatment of these glycoproteins with beta-N-acetylglucosaminidase suppressed their capacity to inhibit this staining. Absorption of anti-CFA serum with asparagine-linked glycopeptides which have the mannose alpha 1,3 arm disubstituted by GlcNAc residues and which have another GlcNAc residue linked beta 1,4 to the beta-linked mannose of the core also inhibited staining for CHAD-1. These data indicated that highly branched asparagine-linked oligosaccharides with terminal GlcNAc residues beta-linked to mannose represent immunoreactive domains of CHAD-1.
Mol Immunol 1987 Jul
PMID:Identification of terminal N-acetylglucosamine residues of highly branched asparagine-linked oligosaccharides as immunoreactive domains of a chicken heterophile antigenic determinant. 244 43

We describe here the properties of a mutant of Chinese hamster ovary cells that expresses a conditional-lethal mutation affecting dense lysosomes. This mutant, termed V.24.1, is a member of the End4 complementation group of temperature-sensitive mutants selected for resistance to protein toxins (Colbaugh, P. A., C.-Y. Kao, S.-P. Shia, M. Stookey, and R. K. Draper. 1988. Somatic Cell Mol. Genet. 14:499-507). Vesicles present in postnuclear supernatants prepared from V.24.1 cells harvested at the restrictive temperature had a 50% reduction in acidification activity, assessed by the ATP-stimulated accumulation of the dye acridine orange in acidic vesicles. To investigate whether specific populations of vesicles were impaired in acidification, we measured acidification activity in three subcellular fractions prepared from Percoll gradients: one containing endosomal and Golgi markers, one containing buoyant lysosomes, and the third containing dense lysosomes. Activity in dense lysosomes was reduced by 90%, activity in the buoyant lysosome fraction was unaffected, and activity in the endosome-Golgi fraction was mildly reduced. The activity of three lysosomal enzymes--beta-hexosaminidase, beta-galactosidase, and beta-glucocerebrosidase--was also reduced in dense lysosomes but nearly normal in the buoyant lysosome fraction. However, beta-hexosaminidase and beta-glucocerebrosidase activity was increased two- to threefold in the endosome-Golgi fraction. We conclude that the lesion selectively impairs dense lysosomes but has little effect on properties of buoyant lysosomes.
 ...
PMID:Impaired lysosomes in a temperature-sensitive mutant of Chinese hamster ovary cells. 252 60

We investigated the effect of exogenous oxygen free radicals and various pH on the release of lysosomal hydrolases from dog myocardial lysosomes. A lysosomal enriched fraction from the homogenate of dog heart was prepared, using differential centrifugation technique. Exogenous oxygen free radicals were generated using xanthine-xanthine oxidase system. The release of lysosomal hydrolases was measured from the lysosomal enriched fraction. There was about 3-fold increase in the release of cathepsin D and beta-N-acetylglucosaminidase activities in the preparations treated with xanthine-xanthine oxidase as compared to those without such treatment. The presence of superoxide dismutase, an oxygen free radical scavenger, prevented the release of cathepsin D and beta-N-acetylglucosaminidase from the lysosomes. Sonication and lubrol treatments, which are known to cause membrane disruption, also induced the release of these enzymes from lysosomal enriched fraction. However, this release was not prevented by superoxide dismutase. The changes in pH (4.5, 5.5, 6.0, 6.5, 7.4, 8.0) alone did not cause any increase in the enzyme release. The presence of oxygen free radicals at each pH resulted in a similar increase in the release of cathepsin D and beta-N-acetylglucosaminidase. These studies suggest that oxygen free radicals and not the alterations in pH are primarily responsible for the release of lysosomal hydrolases. Oxygen free radicals, in addition to their direct myocardial damaging effect, may also be responsible for the cardiac damage through the release of lysosomal enzymes.
J Mol Cell Cardiol 1989 Nov
PMID:Role of oxygen free radicals and pH on the release of cardiac lysosomal enzymes. 260 45

A novel screening procedure was developed for isolating Chinese hamster ovary cell mutants altered in the early steps of the biosynthesis of asparagine-linked glycoproteins. This procedure identifies cells with low intracellular levels of two lysosomal hydrolases, beta-glucuronidase and alpha-iduronidase. One mutant cell line isolated in this way, CHB 11-1-3, has low intracellular levels of seven lysosomal enzymes as compared to wild-type cells. Although CHB 11-1-3 synthesizes mannosylphosphoryldolichol and [Man]5[NAcGlcNH2]2-P-P-lipid, it fails to utilize these lipid intermediates to make normal amounts of [Glc]3[Man]9[NAcGlcNH2]2-P-P-lipid. As a consequence of this glycosylation defect, this mutant transfers oligosaccharides of a different structure than wild type to the lysosomal enzyme beta-hexosaminidase. In addition, it underglycosylates its proteins.
Mol Cell Biochem
PMID:Preliminary characterization of a Chinese hamster ovary cell glycosylation mutant isolated by screening for low intracellular lysosomal enzyme activity. 295 Mar 12

The exoglycosidase, beta-N-acetyl-D-hexosaminidase was purified 600-fold from the muscle-stage larvae (L1) of Trichinella spiralis. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the purified enzyme-active fraction contained 4 polypeptides with apparent molecular weights of 100,000, 68,000, 58,000 and 54,000. The beta-N-acetyl-D-hexosaminidase corresponds to the Mr 100,000 polypeptide as demonstrated by SDS-PAGE analysis of the enzyme-stained region isolated from a non-denaturing polyacrylamide gel. In addition, rabbit antiserum to a homogeneous preparation of the Mr 100,000 polypeptide (isolated by electroelution from an SDS-PAGE gel) specifically immunoprecipitated beta-N-acetyl-D-hexosaminidase activity from an extract of L1. Isoelectrofocusing (pH 3-10) resolved 4 isoenzymes of T. spiralis beta-N-acetyl-D-hexosaminidase with isoelectric points (pI) of 5.35, 5.49, 5.63 and 5.79. The T. spiralis beta-N-acetyl-D-hexosaminidase is a glycoprotein based on its binding to lentil-lectin Sepharose affinity column and its specific binding of concanavalin A on Western blots. The IgG fraction of T. spiralis-infected mouse serum specifically immunoprecipitated T. spiralis beta-N-acetyl-D-hexosaminidase. The removal of carbohydrate from T. spiralis beta-N-acetyl-D-hexosaminidase significantly reduced its antigenicity. Immunocytochemical analysis of L1 tissue sections with polyclonal rabbit antisera to the homogeneous beta-N-acetyl-D-hexosaminidase enzyme indicated localization on cell membranes and the epicuticle.
Mol Biochem Parasitol 1988 Oct
PMID:Purification, characterization, and immunochemical studies of beta-N-acetyl-D-hexosaminidase from the parasitic nematode Trichinella spiralis. 297 30

Trichomonas vaginalis and Tritrichomonas foetus were found to release large amounts of beta-N-acetylglucosaminidase (EC 3.2.1.30), alpha-mannosidase (EC 3.2.1.24), beta-glucosidase (EC 3.2.1.21), acid phosphatase (EC 3.1.3.2) and proteinases during axenic growth in vitro. The enzymes were released continually throughout the growth phase, with the extracellular activity being of the same order as that within the cells. There was differential release of proteinases from Trichomonas vaginalis. The subcellular localization of the hydrolases was determined by differential and isopycnic centrifugation. The intracellular enzymes were shown to be mostly located within particle populations. Centrifugation on Percoll gradients allowed the separation of sub-populations of the particles in T. vaginalis; two distinct sub-populations were apparent with equilibrium densities in 20% (v/v) Percoll of 1.035 and 1.050 g cm-3 respectively. The higher density particles were rich in the hydrolases released most abundantly, suggesting a possible link between enzyme release and these organelles. Distinct subpopulations of hydrolase-containing particles were not detected in Tritrichomonas foetus. The results demonstrate that hydrolytic enzyme release represents a major activity during trichomonad growth.
Mol Biochem Parasitol 1988 Aug
PMID:The release of hydrolases from Trichomonas vaginalis and Tritrichomonas foetus. 314 8

Established renal epithelial cell lines of human, pig, and dog origin (293, LLC-PK1, MDCK) were examined in terms of nephrotoxicity and ability to biotransform cyclosporine A (CsA). All three cell lines exhibited a comparable concentration dependent cytotoxicity to CsA treatment. Alterations in cell function included a decreased transport of lysine, an inhibition of growth, and an activation of lysosomal and mitochondrial activity as indicated by the increased uptake of neutral red (NR) and increased reduction of the tetrazolium dye MTT at 1-6 microM CsA. Increased leakage of lactic dehydrogenase and activities of gamma-glutamyl transpeptidase (GGT) and N-acetyl-beta-D-hexosaminidase were observed at 48 h and 12 microM CsA. A discrimination between CsA and the less nephrotoxic cyclosporine-(CsH) was shown for DNA synthesis and NR uptake. The contribution of extrarenal parameters on kidney cell function was studied by the addition of medium from hepatocytes exposed to CsA to the kidney cell lines. A more potent inhibition of DNA synthesis and enhanced reduction of MTT resulted than by addition of equimolar CsA directly to the kidney cells. These data indicate that hepatocyte constituents present in the medium due to CsA treatment affect kidney cell function; additionally, the presence of CsA metabolites may contribute to the CsA-induced nephrotoxicity. The vascular nephrotoxicity induced by CsA, an increased deposition of platelets in the renal arterioles, was mimicked by cocultures of endothelial cell monolayers and platelets. CsA increased the aggregability and adherence of platelets to the endothelial cell monolayers, whereas CsH had no effect.
Mol Toxicol
PMID:Cyclosporine A nephrotoxicity studied by the combined application of kidney cell lines, hepatocytes, and endothelial-platelet cocultures. 350 90

Latencies and phosphomannosyl-enzyme receptors of lysosomal enzymes were studied in the skeletal muscles of NMRI mice during the appearance (0-1 days) and the repair (3-9 days) of muscle fiber injuries after a single bout of prolonged running (9 hr, 13.5 m/min). The unsedimentable, releasable, and bound activities of arylsulfatase, beta-N-acetylglucosaminidase, beta-D-glucuronidase, cathepsin C, and ribonuclease as well as the content and occupancy of phosphomannosyl-enzyme receptors of lysosomal enzymes were assayed. The distribution of enzyme activities in different fractions as well as the changes after exertion greatly varied between different lysosomal enzymes. In general, the total activities and also the distribution of enzyme activities in different fractions were unaffected 1 hr after exertion, but on the day after exertion small increases were observed in the free and releasable activities. The highest enzyme activities both in the homogenate and in different fractions were recorded 3 days after exertion, after which the activities slowly decreased. The increases of enzyme activities were higher in the free and releasable fractions than in the homogenate but the changes in the proportional distributions of lysosomal enzyme activities between different fractions were minor. The present study also showed the presence of phosphomannosyl-enzyme receptors of lysosomal enzymes in the membranes of skeletal muscles. The total content of phosphomannosyl-enzyme receptors was unchanged 0-3 days after exertion but a small increase occurred 5-8 days after exertion. Instead, the occupancy of these lysosomal receptors with endogenous enzymes was significantly increased 1-5 days after exertion and decreased later to the control level.
Exp Mol Pathol 1984 Dec
PMID:Latencies and phosphomannosyl-enzyme receptors of lysosomal enzymes during the appearance and repair of exercise injuries in mouse skeletal muscles. 609 63


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