scholarly journals Endocytosis of β-N-acetylglucosaminidase from sections of mucolipidosis-II and-III fibroblasts by non-parenchymal rat liver cells

1979 ◽  
Vol 182 (1) ◽  
pp. 245-247 ◽  
Author(s):  
K Ullrich ◽  
K von Figura
Keyword(s):  
Cell Surface ◽  
Rat Liver ◽  
Liver Cells ◽  
Cell Surface Receptors ◽  
Surface Receptors ◽  
Rat Liver Cells ◽  
Mucolipidosis Ii

beta-N-Acetylglucosaminidase isolated from the secretions of fibroblasts of mucolipidosis-II and -III patients is internalized by cultured non-parenchymal rat liver cells. The rate of endocytosis compared with that of beta-N-acetylglucosaminidase from control fibroblasts was 11 and 19% for the enzyme from mucolipidosis-II and -III patients respectively. The inhibition of endocytosis by mannan indicates that the beta-N-acetylglucosaminidase from mucolipidosis-II and -III patients is recognized by cell-surface receptors specific for mannose.

scholarly journals Endocytosis of lysosomal enzymes by non-parenchymal rat liver cells. Comparative study of lysosomal-enzyme uptake by hepatocytes and non-parenchymal liver cells

1979 ◽  
Vol 182 (2) ◽  
pp. 329-335 ◽  
Author(s):  
Kurt Ullrich ◽  
Volkmar Gieselmann ◽  
Günther Mersmann ◽  
Kurt Von Figura
Keyword(s):  
Cell Surface ◽  
Rat Liver ◽  
Lysosomal Enzymes ◽  
High Efficiency ◽  
Indirect Evidence ◽  
Liver Cells ◽  
Cell Surface Receptors ◽  
Surface Receptors ◽  
Parenchymal Liver ◽  
Rat Liver Cells

Cultured non-parenchymal rat liver cells internalize human urine α-N-acetylglucosaminidase, human skin β-N-acetylglucosaminidase and pig kidney α-mannosidase. Different heat-stabilities of endocytosed and endogenous α-mannosidase activity provided indirect evidence that the increase in intracellular activity resulted from uptake. The high efficiency and the saturation kinetics of uptake indicated that these enzymes become internalized by adsorptive endocytosis. Competition experiments with glycoproteins bearing known carbohydrates at their non-reducing terminals, with mannans, methyl glycosides and monosaccharides, established that the uptake of these three lysosomal enzymes is mediated by the binding to cell-surface receptors that recognize mannose and N-acetylglucosamine residues. The decreased uptake after treatment of these enzymes with either β-N-acetylglucosaminidase or α-mannosidase was in accordance with the results of the inhibition experiments. Removal of oligosaccharides of the high-mannose type by treatment with endoglucosaminidase H inhibited uptake almost completely, suggesting that the sugars recognized by cell-surface receptors of non-parenchymal liver cells are located in the outer core of these oligosaccharides. A comparison of the uptake of these three lysosomal enzymes by parenchymal and non-parenchymal rat liver cells indicates that infused α-N-acetylglucosaminidase is taken up preferentially by hepatocytes, whereas α-mannosidase and β-N-acetylglucosaminidase are localized predominantly in non-parenchymal rat liver cells.

Cell-Surface Glycoproteins of Normal and Malignant Rat Liver Cells

1978 ◽  
pp. 412-431
Author(s):  
JAMES J. STARLING ◽  
DOUGLAS C. HIXSON ◽  
SYLVIA C. CAPETILLO ◽  
EDWARD M. DAVIS ◽  
GIOVANNI NERI ◽  
...  
Keyword(s):  
Cell Surface ◽  
Rat Liver ◽  
Liver Cells ◽  
Rat Liver Cells ◽  
Cell Surface Glycoproteins ◽  
Surface Glycoproteins

scholarly journals Extremely rapid endocytosis mediated by the mannose receptor of sinusoidal endothelial rat liver cells

1989 ◽  
Vol 257 (3) ◽  
pp. 651-656 ◽  
Author(s):  
S Magnusson ◽  
T Berg
Keyword(s):  
Cell Surface ◽  
Rat Liver ◽  
Mannose Receptor ◽  
Liver Cells ◽  
Binding Studies ◽  
Receptor Ligand ◽  
Parenchymal Liver ◽  
Rat Liver Cells ◽  
Endocytic Vesicles ◽  
Mannose Receptors

Isolated sinusoidal endothelial rat liver cells (EC) in suspension bound and internalized ovalbumin, a mannose-terminated glycoprotein, in a saturable manner. The binding and uptake were Ca2+-dependent and were effectively inhibited by alpha-methyl mannoside and yeast mannan, but not by galactose or asialoglycoproteins. This corresponds to the binding specificity described for the mannose receptor of macrophages and non-parenchymal liver cells. Binding studies indicated a surface pool of 20,000-25,000 mannose receptors per cell, with a dissociation constant of 6 x 10(-8) M. Uptake and degradation of ovalbumin by isolated EC were inhibited by weak bases and ionophores which inhibit acidification of endocytic vesicles and dissociation of receptor-ligand complexes. Cycloheximide had no effect on uptake or degradation. Degradation, but not uptake, was inhibited by leupeptin. We conclude that ovalbumin dissociates from the mannose receptors in the endosomal compartment and the receptors are recycled to the cell surface, while the ovalbumin is directed to the lysosomes for degradation. A fraction of the internalized ovalbumin was recycled intact to the cell surface and escaped degradation (retroendocytosis). The rate of internalization of ovalbumin by isolated EC was very fast, with a Ke (endocytotic rate constant) of 4.12 min-1, which corresponds to a half-life of 10 s for the surface pool of receptor-ligand complexes. To our knowledge, this is the highest Ke reported for a receptor-mediated endocytosis system.

Role of cell surface receptor mobility in concanavalin A-induced agglutination of Novikoff hepatoma and normal rat liver cells

1980 ◽  
Vol 42 (1) ◽  
pp. 169-182
Author(s):  
P. Mastromarino ◽  
G. Neri ◽  
A. Serra ◽  
E.F. Walborg
Keyword(s):  
Cell Surface ◽  
Rat Liver ◽  
Liver Cells ◽  
Cell Surface Receptor ◽  
Lateral Mobility ◽  
Con A ◽  
Novikoff Hepatoma ◽  
Surface Fluorescence ◽  
Rat Liver Cells ◽  
Normal Rat

The relationshio between Con A-receptor mobility and Con A-induced agglutination of Novikoff hepatoma and normal rat liver cells was investigated. Novikoff cells, incubated with fluorescein-labelled Con A at 3 degrees C displayed uniform, ring-like surface fluorescence. Increasing the temperature of the cells to 37 degrees C caused capping of Con A receptors in approximately 65% of the cells, a phenomenon that could be prevented by prefixing the cells with glutaraldehyde. In spite of these variations in Con A-receptor distribution, Con A-induced agglutination was remarkably constant over a temperature range from 3 to 37 degrees C. In contrast to Novikoff cells, normal hepatocytes displayed a uniform, ringlike surface fluorescence at both 3 and 37 degrees C. No capping was observed. However, hepatocytes, similar to Novikoff cells, were agglutinable by low concentrations of Con A. These findings indicate that, in this model system, Con A-induced cytoagglutination is not dependent upon long-range lateral mobility of Con A receptors. The qualitative differences in the lateral mobility of cell-surface Con A receptors of normal and malignant rat liver cells may represent a marker for neoplastioc transformation during hepatocarcinogenesis, adaptation to growth in ascitic form, or progression of a tumour to a more malignant state.

scholarly journals Interactions of ricin with sinusoidal endothelial rat liver cells. Different involvement of two distinct carbohydrate-specific mechanisms in surface binding and internalization

1991 ◽  
Vol 277 (3) ◽  
pp. 855-861 ◽  
Author(s):  
S Magnusson ◽  
T Berg ◽  
E Turpin ◽  
J P Frénoy
Keyword(s):  
Protein Synthesis ◽  
Cell Surface ◽  
Rat Liver ◽  
Liver Cells ◽  
Surface Binding ◽  
Plant Toxin ◽  
Coated Pits ◽  
Rat Liver Cells ◽  
Mannose Receptors ◽  
Galactosyl Residues

We have investigated the interactions of the plant toxin ricin with sinusoidal endothelial rat liver cells (EC). In these cells, ricin can be bound and internalized via either cell surface galactosyl residues or mannose receptors. Binding and uptake via galactosyl residues and mannose receptors was studied in the presence of mannan (1 mg/ml) and lactose (50 mM) respectively. Whereas most of the ricin binding was accounted for by cell surface galactosyl residues, uptake of ricin via mannose receptors was much more efficient than uptake via galactosyl residues. Internalized ricin is subject to extensive retroendocytosis (recycling to the cell surface from an early endocytic compartment). Retroendocytosis occurs after internalization of ricin via either pathway and to a much greater extent than for other glycoproteins taken up via mannose receptors of the EC. Hyperosmolarity (150 mM-sucrose), which is known to inhibit endocytosis from coated pits, strongly inhibited ricin uptake via mannose receptors, but had less effect on uptake via galactosyl residues. This suggests that only part of the galactose-specific uptake takes place from coated pits. Protein synthesis in EC was very sensitive to ricin [concn. causing half-maximal inhibition (IC50) = 1.3 x 10(-13) M]. Mannan was slightly more effective than lactose in protecting the EC protein synthesis from ricin toxicity.

Effects of Hypophysectomy on the Fine Structure of Rat Liver Cells

1967 ◽  
Vol 25 ◽  
pp. 156-157
Author(s):  
Robert R. Cardell
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Rat Liver ◽  
Liver Cell ◽  
Anterior Pituitary ◽  
Liver Cells ◽  
Biochemical Studies ◽  
Liver Functions ◽  
Rat Liver Cells ◽  
And Control

Hypophysectomy of the rat renders this animal deficient in the hormones of the anterior pituitary gland, thus causing many primary and secondary hormonal effects on basic liver functions. Biochemical studies of these alterations in the rat liver cell are quite extensive; however, relatively few morphological observations on such cells have been recorded. Because the available biochemical information was derived mostly from disrupted and fractionated liver cells, it seemed desirable to examine the problem with the techniques of electron microscopy in order to see what changes are apparent in the intact liver cell after hypophysectomy. Accordingly, liver cells from rats which had been hypophysectomized 5-120 days before sacrifice were studied. Sham-operated rats served as controls and both hypophysectomized and control rats were fasted 15 hours before sacrifice.

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