Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The rat core-specific lectin (CSL) or mannan-binding protein is synthesized and secreted by rat hepatocytes and H-4-II-E hepatoma cells. Prior to secretion proline and lysine residues with collagen-like sequences undergo hydroxylation and subsequent glycosylation of hydroxylysine to produce glucosylgalactosylhydroxylysine. Hydroxylation and subsequent glycosylation are inhibited by alpha,alpha'-dipyridyl (Colley, K. J., and Baenziger, U. U. (1987) J. Biol. Chem. 262, 10290-10295). We have used alpha,alpha'-dipyridyl to investigate the role of hydroxylation and glycosylation on interchain disulfide bond formation, assembly of subunits into high molecular weight complexes, attainment of carbohydrate and lipid binding ability, and secretion. Formation of disulfide-bonded dimers and trimers in the endoplasmic reticulum, assembly into high molecular weight complexes in the Golgi, and attainment of carbohydrate binding activity occur in either the presence or absence of these post-translational modifications. The mature fully processed form of the CSL binds hydrophobic matrices and is secreted at a slow, but linear, rate. Inhibition of proline and lysine hydroxylation and hydroxylysine glycosylation prevents CSL secretion and attainment of binding activity for hydrophobic matrices. Secretion of the lectin, although slow, appears to be an active process and may be related to the capacity to interact with membranes and/or lipids. Other proteins known to contain collagen-like sequences such as acetylcholinesterase, pulmonary surfactant apoproteins, and C1q also interact with lipids and/or membranes. The collagen-like domains of these proteins may also play a role in promoting such interactions.
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PMID:Post-translational modifications of the core-specific lectin. Relationship to assembly, ligand binding, and secretion. 311 40

Hepatocellular carcinoma was induced in rats by administering aflatoxin B1 (AFB1) for 6 weeks. Malignant tumours were preceded by foci and nodules of altered hepatocytes of three histological types, composed of basophilic, eosinophilic, and vacuolated cells. In addition, there were areas of altered hepatocytes that were considered as hyperplastic. Lectins were used as histochemical markers to compare the expression of membrane glycoproteins in hepatocellular carcinomas and hepatic nodules with non-nodular or control hepatocytes. There were marked changes in the lectin-binding patterns of the hepatocellular carcinoma cells and the eosinophilic nodules. The lectin-binding patterns of basophilic nodules, vacuolated nodules, and hyperplastic areas were similar to non-nodular or untreated hepatocytes. The similarity in the lectin-binding changes of the eosinophilic nodules and hepatocellular carcinomas suggests that the eosinophilic nodules may be an early stage in the development of carcinoma.
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PMID:The lectin-binding characteristics of aflatoxin B1 induced lesions in the rat liver. 312 68

Although the separation of water-soluble glycoproteins by high-performance (HP) concanavalin A (ConA) affinity chromatography (AC) is feasible, irregularities may be encountered with hydrophobic glycoproteins. The separation of plasma membrane glycoproteins from liver and Morris hepatoma 7777, used as a model, showed that not only the interaction between the lectin and the oligosaccharide portion of the glycoproteins plays a role in the chromatographic process, but also the hydrophobic interactions between sample and lectin and between sample and support. In this, the characteristics of the support, such as surface hydrophobicity and pore size, play an important part. It was found that a portion of the ConA is not covalently bound to the column, especially when elution is carried out with buffers containing detergents. Moreover, some extremely hydrophobic proteins could only be eluted from the column when high concentrations of detergents [1% (w/v) or higher] were applied. Despite these difficulties, four membrane glycoproteins from the liver with apparent molecular weights of 60, 80, 100 and 110-120 kilodaltons could be highly enriched by ConA HPAC. These proteins were further fractionated according to their strength of binding to the ConA and their different hydrophobic characteristics, using various detergents as eluents.
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PMID:High-performance concanavalin A affinity chromatography of liver and hepatoma membrane proteins. 320 36

A cDNA clone for the chicken liver receptor which mediates endocytosis of glycoproteins containing terminal N-acetylglucosamine has been isolated and sequenced, confirming the previously obtained amino acid sequence of this protein (which is also known as the chicken hepatic lectin). This cDNA was introduced into Rat-1 fibroblasts and expressed using the promotor in the long terminal repeat of Moloney murine leukemia virus. Cells expressing chicken receptor were identified by screening with antireceptor antibodies followed by fluorescein-conjugated second antibodies. Receptor expressed in these cells was indistinguishable on gel electrophoresis from receptor isolated from liver. Three clonally isolated lines were examined for their ability to bind agalacto-alpha 1-acid glycoproteins at 0 degrees C and to take up and degrade this ligand at 37 degrees C. The receptor number (50,000/cell), affinity for ligand (35 nM), and uptake rate (5 molecules ligand/surface receptor/h) are similar to those previously observed for chicken hepatocytes, and for the uptake of asialoglycoproteins by rat hepatocytes and hepatoma cells. These findings indicate that the chicken receptor correctly traverses the endocytic pathway in a rat cell even though the cytoplasmic domain of this protein shows no primary structural homology with the corresponding portion of the rat liver receptor or with receptors found in fibroblasts.
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PMID:Endocytosis of N-acetylglucosamine-containing glycoproteins by rat fibroblasts expressing a single species of chicken liver glycoprotein receptor. 328 41

When rat hepatoma cells (R-Y121B) were first incubated with labeled insulin, followed by concanavalin A, at 500 micrograms/ml at 23 degrees C, the total cell-associated radioactivity increased. At 4 degrees C, however, this increase was not observed. Scatchard analysis revealed that concanavalin A increased insulin binding affinity. The bound insulin was internalized together with concanavalin A. When the cells were incubated with concanavalin A prior to insulin addition, however, the total cell-associated radioactivity decreased at both temperatures. This was caused by the masking of insulin binding sites by the lectin.
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PMID:Concanavalin A changes not only the number of insulin binding sites but also the binding affinity in rat hepatoma cells in culture. 330 91

Lectin binding [concanavalin A, biotinylated ricinus communis agglutinin, and biotinylated succinylated wheat germ agglutinin (B-SWGA)] was used to detect the glycosylated proteins associated with a residual protein fraction [insoluble in 4% sodium dodecyl sulfate and termed the nuclear residual fraction (NRF)] or with nuclear matrix preparations from normal rat liver, azo dye (3'-MeDAB)-induced rat hepatoma, and Walker 256 transplantable carcinosarcoma. One- and two-dimensional gel electrophoresis were used with lectins, polyclonal antisera, and monoclonal antibody binding to characterize some of the glycoconjugates. Two polypeptide bands with approximate molecular weights of 95,000 and 55,000, shown previously to be present only in the induced tumor cells and the Walker 256 tumor, were reactive with lectins. In addition, a Mr 62,000 protein reacted only with B-SWGA in the nuclear matrix fractions from normal rat liver and the induced hepatoma. A polypeptide band (approximate molecular weight, 213,000) in the Walker 256 NRF reacted with concanavalin A and biotinylated ricinus communis agglutinin. One polypeptide band (approximate molecular weight, 182,000) reacted with concanavalin A in all three tissues, with biotinylated ricinus communis agglutinin and B-SWGA in the Walker NRF, and with B-SWGA in the hepatoma NRF. Another polypeptide band (approximate molecular weight, 138,000), reactive with all three lectins, was present in all three tissues. Our findings are consistent with previous reports of lectin binding proteins in the eukaryotic cell nucleus and indicate that certain glycoproteins isolated in nuclear preparations are found specifically in 3'-MeDAB-induced hepatoma and Walker 256 transplantable carcinosarcoma.
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PMID:Lectin-binding proteins in nuclear preparations from rat liver and malignant tumors. 333 20

The lectin wheat germ agglutinin (WGA), which has been reported to inhibit nuclear protein uptake in vitro by isolated nuclei (Finlay et al. (1987) J. Cell Biol. 104, 189), also blocks, on microinjection into living cells, the migration of proteins into the cell nucleus. Radioactively labeled nuclear proteins were injected into the cytoplasm of Xenopus oocytes and their reentry into the nucleus was analyzed in the presence or absence of WGA by two-dimensional gel electrophoresis. In another set of experiments, fluorescently labeled nucleoplasmin was injected, alone or together with WGA, into the cytoplasm of rat hepatoma cells, and its nucleocytoplasmic distribution was studied by quantitative laser fluorescence microscopy. The results indicate that WGA inhibits the uptake of karyophilic proteins in general, independent of their sizes. Since the nucleocytoplasmic flux of a dextran with Mr 10,000 was not affected it can be excluded that WGA acts by a general blockade or constriction of the functional pore channel. At reduced WGA concentrations, the rate but not the final extent of nuclear protein accumulation was decreased. These findings support the concept that the O-glycosidically bound carbohydrates of certain nuclear pore complex proteins are exposed to the pore interior and that these regions are probably involved in nucleocytoplasmic translocation processes.
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PMID:Inhibition of nuclear accumulation of karyophilic proteins in living cells by microinjection of the lectin wheat germ agglutinin. 333 28

Treatment of H4 hepatoma cells with the lectin wheat germ agglutinin (WGA) in the concentration range of 10-25 micrograms/ml increased 125I-insulin binding fivefold as compared to control binding in untreated cells. The increased insulin binding was rapid, readily reversible, and correlated with a 10-fold increase in the binding affinity of the receptor for insulin. Kinetic studies indicate that this increased affinity resulted from a decrease in the dissociation rate. The effect was specifically mediated by the lectin since it was reversed by simultaneous incubation with the monosaccharide N-acetyl-D-glucosamine (50 mM) or the disaccharide N,N'-diacetylchitobiose (1 mM). The WGA-mediated increase in insulin binding was not caused by inhibited insulin degradation. While WGA (5 micrograms/ml) mimicked insulin to induce stimulated uptake of [3H]aminoisobutyrate, the lectin failed to enhance the biological sensitivity of H4 hepatoma cells to insulin. At higher concentrations of WGA (125 micrograms/ml), interference with the insulin-mediated response was observed. Trypsin treatment of H4 hepatoma cells prior to measuring binding of 125I-insulin in the presence of increasing concentrations of native insulin, led to a leftward shift of the competition curve, indicating an increased affinity of the receptor. No further increase was observed when the trypsin-treated cells were subsequently exposed to WGA. These results suggest that trypsin treatment and WGA exposure may increase the affinity of the receptor by a similar mechanism. The results are consistent with the concept that WGA and trypsin decrease interaction between insulin binding and receptor affinity regulating components in the plasma membrane, leading to an increase in the affinity of the receptor for insulin.
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PMID:Insulin receptor regulation in minimal deviation hepatoma cell line. 352 5

A variety of animal tissues contain beta-galactoside-binding lectins with molecular masses in the range 13-17 kDa. There is evidence that these lectins may constitute a new protein family although their function in vivo is not yet clear. In this work the major part of the amino acid sequence of the 13 kDa lectin from bovine heart muscle has been determined. Comparison of this sequence with the cDNA-deduced sequence published for the chick embryo skin lectin showed 58% homology. Comparison of the bovine lectin sequence with partial sequences from two cDNA clones from a human hepatoma library and partial amino acid sequences of human lung lectin showed 70, 40 and 85% homology, respectively. The sequences of these vertebrate lectins are thus clearly related, supporting earlier results of immunological cross-reactivity within this group of proteins. Computer searching of protein sequence databases did not detect significant homologies between the bovine lectin sequence and other known proteins.
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PMID:Amino acid sequence of beta-galactoside-binding bovine heart lectin. Member of a novel class of vertebrate proteins. 356 27

The core-specific lectin (CSL) synthesized and secreted by rat hepatocytes and the rat hepatoma H-4-II-E shows affinity for mannose and N-acetylglucosamine residues in the "core" region of asparagine-linked oligosaccharides. The CSL undergoes two stages of post-translational modification which result in an increase in its Mr from 24,000 to 26,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We have determined that the lectin undergoes hydroxylation of proline and lysine and that the hydroxylysine is glycosylated to form glucosylgalactosylhydroxylysine (GlcGalHyLys). CSL metabolically labeled with [3H]lysine and [3H]proline contains hydroxylated forms of proline and lysine. The mature form of the lectin can also be metabolically labeled with [3H]galactose. alpha,alpha'-Dipyridyl, an inhibitor of collagen prolyl and lysyl hydroxylases, prevents the metabolic incorporation of [3H]galactose and the post-translational increases in the Mr of the CSL, indicating that both events are dependent upon hydroxylation of proline and lysine. Virtually all of the hydroxylysine present in the CSL is recovered as glucosylgalactosylhydroxylysine after alkaline hydrolysis. The post-translational modifications of the CSL place it in a select family of secreted proteins which contain collagen-like sequences, including the pulmonary surfactant proteins, complement component C1q, and the 18 S asymmetric form of acetylcholinesterase.
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PMID:Identification of the post-translational modifications of the core-specific lectin. The core-specific lectin contains hydroxyproline, hydroxylysine, and glucosylgalactosylhydroxylysine residues. 361 Oct 62


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