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 propeptides of lysosomal enzymes have been implicated in membrane association and mannose 6-phosphate-independent sorting to the lysosome (Rijnboutt, S., Aerts, H., Geuze, H. J., Tager, J. M., and Strous, G. J. (1991) J. Biol. Chem. 266, 4862-4868; McIntyre, G. F., and Erickson, A. H. (1991) J. Biol. Chem. 266, 15438-15445). In this report, the function of the propeptide of procathepsin D in sorting to the lysosome was directly assessed using a cathepsin D deletion mutant lacking the propeptide, and using a chimeric cDNA encoding the cathepsin D propeptide fused to the secretory protein alpha-lactalbumin. Proteins encoded by these cDNAs were expressed in mouse Ltk- cells and in human hepatoma Hep G2 cells, and then immunoprecipitated and analyzed by SDS-polyacrylamide gel electrophoresis. The deletion mutant was glycosylated but was rapidly degraded in a chloroquine-independent fashion and did not assume an active conformation. Thus the propeptide appeared to be necessary for correct folding. The chimeric protein was glycosylated and secreted. The coincidence of complex oligosaccharide modification and secretion of the chimeric protein suggested that it was slowly released from the endoplasmic reticulum and rapidly passed through the cell to the extracellular compartment. This was confirmed by immunofluorescent localization of the proteins. The data indicated that the propeptide appeared to be necessary for folding of cathepsin D but, unlike the yeast vacuolar propeptides, was not sufficient to direct a secretory protein to the lysosome in fibroblasts or in epithelial cells.
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PMID:The role of the cathepsin D propeptide in sorting to the lysosome. 140 Apr 84

To determine the cause of the increased content of carbohydrate-bound phosphate in tumour lysosomal hydrolases, the activity and kinetics in human hepatocellular carcinoma of two enzymes involved in the formation of mannose-6-phosphate in lysosomal hydrolases UDP-GlcNAc: lysosomal enzyme GlcNAc alpha l-phosphotransferase (GlcNAc-phosphotransferase) and phosphodiester glycosidase were studied. The activity level of the phosphotransferase with artificial and natural substrates was elevated (P less than 0.025 and P less than 0.001, respectively) in hepatoma compared to that in uninvolved tissue, while the phosphodiester glycosidase of hepatoma was at a level similar to that of the uninvolved tissue. To verify a previous observation that cathepsin D of human hepatoma contained increased GlcNAc-phosphomannose, the protease was examined for carbohydrate phosphorylation by the GlcNAc-phosphotransferase. The protease from normal human liver was much more phosphorylated than hepatoma protease, confirming the previous observation. The predominant phosphorylation of the protease occurred in one of two major heavy subunits, with some phosphorylation in one of two minor light subunits.
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PMID:Elevated carbohydrate phosphotransferase activity in human hepatoma and phosphorylation of cathepsin D. 164 48

We have studied the role of N-linked oligosaccharides and proteolytic processing on the targeting of cathepsin D to the lysosomes in the human hepatoma cell line HepG2. In the presence of tunicamycin cathepsin D was synthesized as an unglycosylated 43-kDa proenzyme which was proteolytically processed via a 39-kDa intermediate to a 28-kDa mature form. Only a small portion was secreted into the culture medium. During intracellular transport the 43-kDa procathepsin D transiently became membrane-associated independently of binding to the mannose 6-phosphate receptor. Subcellular fractionation showed that unglycosylated cathepsin D was efficiently targeted to the lysosomes via intermediate compartments similar to the enzyme in control cells. The results show that in HepG2 cells processing and transport of cathepsin D to the lysosomes is independent of mannose 6-phosphate residues. Inhibition of the proteolytic processing of 53-kDa procathepsin D by protease inhibitors caused this form to accumulate intracellularly. Subcellular fractionation revealed that the procathepsin D was transported to lysosomes, thereby losing its membrane association. Procathepsin D taken up by the mannose 6-phosphate receptor also transiently became membrane-associated, probably in the same compartment. We conclude that the mannose 6-phosphate-independent membrane-association is a transient and compartment-specific event in the transport of procathepsin D.
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PMID:Mannose 6-phosphate-independent targeting of cathepsin D to lysosomes in HepG2 cells. 166 Aug 78

Using a sandwich enzyme-linked immunoassay, plasma total cathepsin D concentration was assayed in 40 breast cancer patients and 84 patients with various liver diseases and compared to that of 52 normal subjects. There were no significant variations found in breast cancer patients related to tumor size, node invasiveness or metastases. In normal women, cathepsin D levels were slightly but not significantly increased in the luteal phase and in pregnancy. By contrast, plasma cathepsin D concentration was significantly increased in 70-75% of patients with liver disease (cirrhosis, hepatocarcinoma, hepatitis), but not in those with liver steatosis. Cathepsin D was independent of most of the plasma hepatic function tests and was correlated with alpha-fetoprotein in cirrhosis and with alpha-fucosidase in primary hepatocellular carcinoma. We conclude that plasma cathepsin D is not a useful marker in breast cancer. However, since the cellular level of this protease is associated with risk of metastasis in breast cancer, clinical follow-up will be required to test whether high cathepsin D plasma concentration has any prognostic value in liver cirrhosis and primary hepatocarcinoma.
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PMID:Increased plasma cathepsin D concentration in hepatic carcinoma and cirrhosis but not in breast cancer. 166 31

The synthesis and secretion of fibronectin (FN) was observed in 4 human hepatocellular carcinoma (HCC)-derived cell lines using a serum-free conditioned medium. It was also demonstrated that FNs secreted from these cell lines (HCC-FN) were structurally altered compared to plasma FN produced by normal hepatocytes. Using limited proteolysis with cathepsin D followed by immunoblot analysis with a carboxy-terminal specific antibody, the existence of an extra domain (ED) segment in the carboxy-terminal region of HCC-FNs was confirmed. Expression of the additional nucleotide insert (ED sequence), which is reported to be absent in hepatocyte mRNA and is characteristic of cellular FN-mRNA, was confirmed in mRNA from all 4 HCC cell lines. It is now evident that HCC cells secrete different variants of FN compared with normal hepatocytes due to alternative splicing of mRNA precursors. This differential RNA processing seems to be one of the phenotypic alterations associated with the oncogenic transformation of hepatocytes.
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PMID:Structural alterations in fibronectins secreted from 4 human hepatoma cell lines: demonstration of hepatoma-associated alternative splicing of mRNA precursors. 166 73

Two enzymes (N-acetylglucosamine-1-phosphotransferase and phosphodiester glycosidase) involved in formation of mannose-6-phosphate at lysosomal hydrolases were studied for the activity and kinetics in human hepatocellular carcinoma. The activity level of the phosphotransferase with an artificial substrate was elevated (p less than 0.025) in hepatoma compared to that in normal liver, while the phosphodiester glycosidase of hepatoma was in a similar level with that of control. The elevation was more remarkable with a physiological substrate, cathepsin D. (P less than 0.001). Since cathepsin D from normal liver was previously demonstrated to contain less phosphomannose compared to the hepatoma protease, the protease was investigated for carbohydrate phosphorylation by the phosphotransferase. The liver protease was much more phosphorylated than the hepatoma protease, endorsing the previous observation. The predominant phosphorylation of the protease occurred in heavy subunit.
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PMID:[Carbohydrate phosphotransferase in human hepatoma and phosphorylation of cathepsin D]. 217 73

A significant elevation of cathepsin D activity was observed in six human hepatoma tissues as compared to 12 normal human livers. In isoelectric focusing experiments, cathepsin D purified from normal liver exhibited three different forms, with isoelectric points of 5.6, 6.1, and 6.7, while cathepsin D purified from hepatoma contained another five to six more acidic forms in addition to the forms observed in normal liver cathepsin D. When the tumor enzyme was treated with endo-beta-N-acetylglucosaminidase H followed by isoelectric focusing, the acidic components disappeared and were converted to forms identical to those of the normal liver cathepsin D. Determination of the mannose-6-phosphate content showed that hepatoma cathepsin D contains twice as much mannose-6-phosphate as normal liver cathepsin D. Peptide mapping and amino acid analysis showed that the protein moiety of cathepsin D from hepatoma is almost identical with that from normal liver. These findings indicate that the appearance of acidic variants in hepatoma cathepsin D is mainly due to changes in the oligosaccharide chains of the enzyme, which are closely associated with the increase of mannose-6-phosphate in the tumor enzyme.
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PMID:Elevated activity and increased mannose-6-phosphate in the carbohydrate moiety of cathepsin D from human hepatoma. 282 73

Cathepsin D was purified to apparently homogeneous form from normal human liver and hepatoma. The purified enzyme could not be distinguished between normal liver and hepatoma in terms of specific activity, subunit composition, antigenicity, amino acid composition and tryptic peptides. However, the hepatoma enzyme exhibited more charge heterogeneity to give multiple acidic variant forms which were devoid or much less in the normal liver enzyme. When the hepatoma enzyme was treated with endo-beta-N-acetylglucosaminidase H, the acidic variant forms disappeared and were converted into forms identical to those of normal liver. The content of mannose-6-phosphate in the hepatoma enzyme was twice as much as that in the normal liver enzyme. Thus, charge heterogeneity found in hepatoma cathepsin D is ascribed to increased phosphorylation on oligosaccharides bound to the enzyme, most probably due to cancer-associated, impaired processing in carbohydrate moiety. A significant elevation of cathepsin D activity per tissue proteins was observed in hepatoma as compared to normal liver. In contrast, true specific activity per cathepsin D protein in hepatoma was significantly lowered than that of normal liver. The lower true specific activity in hepatoma tissue may be attributed to an increased content in an inactive, large-molecular precursor form of the enzyme.
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PMID:[Tumor-associated impairment of the processing of hepatoma cathepsin D]. 283 81

The synthesis, transport and processing of lysosomal enzymes was examined in human hepatoma HepG2 cells and in human fibroblasts exposed to the Golgi alpha-mannosidase I inhibitor 1-deoxy-manno-nojirimycin. In HepG2 cells cathepsin D, beta-hexosaminidase and arylsulfatase B synthesized in the presence of 5 mM 1-deoxy-manno-nojirimycin contained exclusively endo-beta-N-acetylglucosaminidase H-cleavable oligosaccharides, indicating that alpha-mannosidase I had been inhibited efficiently. The proteolytic processing of intracellularly retained cathepsin D was retarded and the fraction of secreted cathepsin D was increased two-fold. In fibroblasts neither segregation nor maturation of cathepsin D were affected by 1-deoxy-manno-nojirimycin in spite of the inhibition of oligosaccharide processing. In the presence of the glucosidase I inhibitor 1-deoxynojirimycin, the precursor of cathepsin D (larger by about 1 kDa than the secreted form) accumulated transiently in light membranes in HepG2 cells. Release from the site of accumulation was accompanied by a decrease in size by about 1 kDa. This change was attributed to the removal of glucose residues. In fibroblasts the transient accumulation of larger precursors in the presence of 1-deoxynojirimycin was more pronounced than in HepG2 cells. The differential effects of alpha-mannosidase I and glucosidase I inhibitors on the transport of cathepsin D in HepG2 cells and fibroblasts may indicate that different intermediates in the biosynthetic pathway of asparagine-linked oligosaccharides participate in the transport of lysosomal enzymes in the two cell types.
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PMID:Cell type dependent inhibition of transport of cathepsin D in HepG2 cells and fibroblasts exposed to deoxy-manno-nojirimycin and deoxynojirimycin. 293 77

Human hepatoma cell (HepG2) or rabbit hepatocyte monolayers were incubated with [35S]methionine in presence or absence of tunicamycin, a potent inhibitor of asparagine-linked glycosylation. The 35S-labeled nonglycosylated and control fibrinogens purified from the media were used to evaluate the influence of the oligosaccharide on the catabolic properties of this glycoprotein. Plasmin, pronase, cathepsin D or cathepsin B each degraded the nonglycosylated and control fibrinogens similarly, as evidenced by the release of trichloroacetic acid-soluble radioactivity and by SDS-polyacrylamide gel electrophoresis and autoradiography of plasmic digests. Nonglycosylated and control fibrin clots also showed no differences in susceptibility to plasmic digestion. The two forms of fibrinogen demonstrated the same plasma half-life in rabbits. These data indicate that the oligosaccharide does not influence the proteolytic stability or the in vivo plasma survival of fibrinogen, and suggest that other biochemical determinants may influence the catabolic properties of this molecule.
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PMID:Catabolic properties of aglycofibrinogen synthesized by tunicamycin-treated human hepatoma (HepG2) cells and rabbit hepatocytes. 301 19


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