Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human serum contains lectins which inhibit the uptake of mannose- and N-acetylglucosamine-terminated glycoproteins by isolated rat hepatic sinusoidal cells. In these experiments, calcium-dependent and calcium-independent human serum mannose-binding proteins have been isolated by affinity chromatography using mannan linked to four different supports. In electroblots both calcium-dependent and -independent serum mannose-binding proteins bound radioiodinated mannan and invertase in the presence of calcium ions, but the binding of calcium-dependent serum mannose-binding proteins was abolished by EDTA. Chicken antibodies were raised against serum mannose-binding proteins and an ELISA was developed. The principal calcium-independent serum mannose-binding protein is mannose-specific IgG as judged by immunodiffusion and electroblotting with anti-human IgG antibodies. The calcium-dependent serum mannose-binding protein is probably the secreted form of an intracellular hepatocyte mannose-binding protein since: antibodies raised against the 30 kDa subunit of the calcium-dependent serum mannose-binding protein also bound 30 kDa subunits of whole liver homogenate and purified human liver mannose-binding protein; antibodies to the human liver mannose-binding protein bound to the 30 kDa subunit of the calcium-dependent serum mannose-binding protein; and the binding specificities of the calcium-dependent serum mannose-binding protein for N-acetylglucosamine and fucose as well as mannose, and its recognition of the core region of an oligosaccharide rather than only the peripheral sugars, were identical to those reported for the hepatocyte mannose-binding protein. The physiological ligands of these serum mannose-binding proteins are unknown but they could bind noxious glycoproteins which enter the circulation prior to their removal by the sinusoidal mannose receptor.
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PMID:Mannose-binding proteins in human serum: identification of mannose-specific immunoglobulins and a calcium-dependent lectin, of broader carbohydrate specificity, secreted by hepatocytes. 374 82

Previous studies have suggested that a mannose receptor mediates the phagocytic uptake of effete rod outer segments by retinal pigment epithelial cells. In the present study, the effect of adding a soluble ligand for the mannose receptor, horseradish peroxidase, was examined. Cultured retinal pigment epithelial cells from Long Evans rats were preincubated with various concentrations of horseradish peroxidase for 20 min followed by a challenge of FITC-labeled bovine rod outer segments for 3 h. Both counts of total rod outer segments (bound and ingested) and ingested rod outer segments were determined. Rod outer segment uptake was reduced, in a concentration-dependent fashion, by an average of 60% of control values when horseradish peroxidase was added to retinal pigment epithelial cultures. Similarly, total rod outer segment values were reduced to 50% of controls in the presence of at least a 10 micrograms ml-1 horseradish peroxidase concentration. Horseradish peroxidase inhibition of retinal pigment epithelial phagocytic capacity was reversible. Other high mannose glycoproteins, such as invertase, beta-glucoronidase, and ovalbumin, were equally effective in preventing rod outer segment ingestion by retinal pigment epithelial cells. These data further support the hypothesis that a mannose receptor on the retinal pigment epithelial apical surface facilitates phagocytosis of rod outer segments.
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PMID:Natural, high-mannose glycoproteins inhibit ROS binding and ingestion by RPE cell cultures. 854 90

Using fluorescein isothiocyanate-conjugated ovalbumin (OVA-FITC), 125I-mannan, or 125I-invertase as specific ligands for the mannose receptor, we have quantified its activity in mouse and rat hepatic sinusoidal endothelium (HSE), under both basal conditions and after lipopolysaccharide (LPS) or human recombinant interleukin-1beta (IL-1beta) stimulations. Mouse treatment for 4 hours with 5 microg/kg IL-1beta significantly increased OVA-FITC uptake by HSE. Ligand uptake exhibited a sublobular compartmentalization: In control mice as well as in IL-1beta-stimulated mice, the ligand distributed preferentially in the periportal and septal areas; no OVA-FITC was observed in the perivenous sinusoids. In vitro exposure of mouse HSE to 100 pg/mL LPS or 1 ng/mL IL-1beta for 6 hours significantly (P < .01) increased OVA-FITC uptake. Blocking IL-1 receptors in HSE by addition of 100 ng/mL IL-1 receptor antagonist (IL-1Ra) before stimulation with LPS or IL-1beta abrogated the increase in mannose receptor-mediated uptake. In vitro endocytosis assays showed that rat HSE uptake of 125I-mannan or 125I-invertase progressively increased with both exposure time and concentration of added IL-1beta. Upregulation of mannose receptor-mediated uptake in response to IL-1beta or LPS was also blocked by previous addition of IL-1Ra to rat HSE. Flow cytometric analysis showed a significant HSE heterogeneity in mannose receptor-mediated endocytosis in response to IL-1beta treatment: type I endothelial cells (EC-I, defined by their small size and high cytoplasmic density) significantly (P < .01) increased OVA-FITC uptake compared with type II endothelial cells (EC-II, defined by their large size and low cytoplasmic density). In addition, the subset of EC-I contained three times more IL-1beta-binding cells than the EC-II subset. Because EC-I and EC-II are preferentially located in the periportal and perivenous segments of hepatic sinusoids, respectively, these results suggest that IL-1beta, apart from upregulating mannose receptor activity, contributes to the sublobular compartmentalization of this endothelial cell function.
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PMID:Hepatic sinusoidal endothelium heterogeneity with respect to mannose receptor activity is interleukin-1 dependent. 867 73

Mannose-receptor-mediated clearance of circulating glycoproteins was studied in Atlantic cod (Gadus morhua). Distribution studies with radioiodinated and fluorescently labelled ligands showed that cod liver lysosomal alpha-mannosidase and yeast invertase were rapidly eliminated from blood via a mannose specific pathway in liver parenchymal cells and endocardial endothelial cells of atrium and ventricle. Asialo-orosomucoid, a galactose-terminated glycoprotein, was cleared by liver only. In vitro studies were performed with primary cultures of atrial-endocardial endothelial cells (AEC), incubated at 12 degrees C in a serum free medium. Cod AEC endocytosed mannose-terminated glycoproteins (125I-alpha-mannosidase, 125I-invertase, 125I-mannan, 125I-ovalbumin and unlabelled lysosomal alpha-mannosidase), whereas 125I-asialo-orosomucoid was not recognised. Uptake of radiolabelled mannose-terminated ligands was inhibited 80-100% in the presence of excess amounts of mannan, invertase, D-mannose, L-fucose or EGTA. Our results suggest that the cod endocardial endothelial cells express a specific Ca(2+)-dependent mannose receptor, analogous to the mannose receptor on mammalian macrophages and liver sinusoidal endothelial cells.
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PMID:Mannose-receptor-mediated clearance of lysosomal alpha-mannosidase in scavenger endothelium of cod endocardium. 1142 31

Knowing that human blood monocyte-derived dendritic cells express cell-surface mannose-specific lectins, we prepared various mannoses containing glycoconjugates with the aim of developing highly specific synthetic carriers of oligonucleotides and genes. Conjugates were prepared from oligosaccharides obtained by hydrazinolysis of Saccharomyces cerevisiae invertase glycopeptides. The reducing saccharides were converted into glycosynthons, i.e., into glyco-amino acids. Fluorescein derivatives were obtained by coupling the free carboxyl group of oligosaccharyl-pyroglutamate to the alpha-amino group of epsilon-fluoresceinyl-thiocarbamyl lysine methyl ester. It has been shown by others that glycosylated linear oligolysines containing up to six alpha-D-mannopyranosylphenylthiocarbamyl units have a high affinity for the human mannose receptor. In order to obtain fully biodegradable clusters and to improve both the specificity and the selectivity, disaccharides transformed into glycosynthons were coupled to pentalysine carriers (Lys5-Ala-Cys-NH2). Glycosylated pentalysyl cysteine conjugates were made fluorescent upon substitution of the cysteine thiol group with fluorescein iodoacetamide. As shown by flow cytofluorimetry, both the dimannoside clusters and yeast oligomannosides were very efficiently taken up by DC, conversely lactoside clusters were not.
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PMID:Uptake of dimannoside clusters and oligomannosides by human dendritic cells. 1216 31