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 intracellular pathways taken by galactose-terminal glycoproteins were examined following endocytosis by the asialoglycoprotein receptor in monolayers of the human hepatoma cell line, Hep G2. In addition to a pathway leading to lysosomal degradation, single cohort kinetics revealed that up to 28% of surface-bound and internalized 125I-asialoorosomucoid (ASOR) eventually returned undegraded to the extracellular medium over 6 hr in the presence or absence of free ASOR in the exocytosis medium. This reappearance of ligand in the exocytosis medium represented a constant fraction of surface bound and internalized 125I-ASOR, and followed pseudo-first order kinetics with t1/2 = 84 min (long transit pool). Under conditions of enhanced ligand-receptor dissociation (incubation with 100 mM N-acetylgalactosamine (GalNAc), at least 50% of initially internalized 125I-ASOR returned to the cell surface as ligand-receptor complexes, followed by dissociation of free ligand into the exocytosis medium. This rapid transit pool of ligand also displayed pseudo-first order kinetics with t1/2 = 24 min. Exocytosis of 125I-Gal-cytochrome c, a synthesized ligand displaying rapid dissociation from the asialoglycoprotein receptor (ASGP-R), paralleled the kinetics of the rapid transit pool of 125I-ASOR (t1/2 = 28 min). Furthermore, in addition to spontaneous dissociation from ASPG-R following return to the cell surface, studies conducted in saponin-permeabilized monolayers support the return of free intracellular 125I-Gal-cytochrome c to the cell surface during exocytosis. The rapid transit pool of ligand was insensitive to inhibition by 10 mM sodium azide or 0.1 mM primaquine. In contrast, the long transit pool destined for exocytosis was inhibited 50% by 10 mM sodium azide, but insensitive to inhibition by 0.1 mM primaquine. These data suggest that, following internalization by the ASGP-R, a major pathway of ligand movement includes the rapid return of ligand-receptor complexes and/or free ligand to the cell surface. Return of ligand-receptor complexes or free ligand to the cell surface occurs prior to an acidic sorting compartment, can involve multiple cycles of return to the cell surface, and may involve passage through other nonlysosomal intracellular organelles.
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PMID:Cellular pathways of galactose-terminal ligand movement in a cloned human hepatoma cell line. 609

The asialoglycoprotein receptor has been identified on a continuous human hepatoma cell line, HepG2. This receptor requires Ca2+ for ligand binding and is specific for asialoglycoprotein. There are approximately 150,000 ligand molecules bound/cell at 4 degrees C. These receptors represent a homogeneous population of high affinity binding sites with Kd = 7 X 10(-9) M. From the rate of 125I-ASOR binding at 4 degrees C, kon was 0.95 X 10(6) M-1 min-1. Uptake of 125I-ASOR at 37 degrees C was approximately 0.02 pmol/min/10(6) cells.
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PMID:Characterization of the asialoglycoprotein receptor in a continuous hepatoma line. 626 54

The asialoglycoprotein receptor (ASGP-R) isolated from human liver is a single polypeptide of Mr = 46,000. Monospecific polyclonal anti-human ASGP-R antibodies as well as anti-rat ASGP-R antibodies specifically inhibit binding of 125I-asialoorosomucoid to human hepatoma Hep G2 ASGP-R. These anti-ASGP-R antibodies specifically immunoprecipitate the 46,000-Da polypeptide from hepatoma cells labeled biosynthetically with 35S-amino acid. The receptor is initially synthesized as a 40,000-Da precursor which is converted to the mature 46,000-Da species with a t1/2 of approximately 45 min. The precursor species is sensitive to endo-beta-N-acetylglucosaminidase H and becomes resistant coincident with the appearance of the mature 46,000-Da receptor. In addition, the receptor synthesized in the presence of tunicamycin is approximately 34,000 Da. The newly synthesized ASGP-R reaches the cell surface after 45-60 min, where only the mature 46,000-Da species is present. In Hep G2 cells, the ASGP-R has a mean lifetime of approximately 30 h, a value which is unaltered during maximal rates of receptor-mediated endocytosis of ASGP.
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PMID:Biosynthesis of the human asialoglycoprotein receptor. 630 39

Receptor-mediated uptake and degradation of 125I-asialoorosomucoid (ASOR) in human hepatoma HepG2 cells is inhibited by the lysosomotropic amines chloroquine and primaquine. In the absence of added ligand at 37 degrees C, these amines induce a rapid (t1/2 5.5-6 min) and reversible loss of cell surface 125I-ASOR binding sites as well as a rapid decrease in 125I-ASOR uptake and degradation. There is no effect of these amines on the binding of 125I-ASOR to the cell surface at 4 degrees C or on the rate of internalization of prebound 125I-ASOR. The loss of 125I-ASOR surface binding at 37 degrees C is not attributable to altered affinity of ligand-receptor binding. In the presence of added ligand at 37 degrees C, there is a more rapid (t1/2 2.5-3 min) loss of hepatoma cell surface receptors. In addition, the amines inhibit the rapid return of the internalized receptor to the cell surface. We examined the nature of this loss of 125I-ASOR surface binding sites by following the fate of receptor molecules after biosynthetic labeling and after cell surface iodination. At 37 degrees C, chloroquine and primaquine induce a loss of asialoglycoprotein receptor molecules from the hepatoma cell surface to an internal pool.
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PMID:Recycling of the asialoglycoprotein receptor and the effect of lysosomotropic amines in hepatoma cells. 631 32

With few exceptions, receptor-mediated endocytosis of specific ligands is mediated through clustering of receptor-ligand complexes in coated pits on the cell surface, followed by internalization of the complex into endocytic vesicles. During this process, ligand-receptor dissociation occurs, most probably in a low pH prelysosomal compartment. In most cases the ligand is ultimately directed to the lysosomes, wherein it is degraded, while the receptor recycles to the cell surface. We have studied the kinetics of internalization and recycling of both the asialoglycoprotein receptor and the transferrin receptor in a human hepatoma cell line. By employing both biochemical and morphological/immunocytochemical approaches, we have gained some insight into the complex mechanisms which govern receptor recycling as well as ligand sorting and targeting. We can, in particular, explain why transferrin is exocytosed intact from the cells, while asialoglycoproteins are degraded in lysosomes. We have also localized the intracellular site at which endocytosed receptor and ligand dissociate.
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PMID:Sorting and recycling of cell surface receptors and endocytosed ligands: the asialoglycoprotein and transferrin receptors. 632 36

The human asialoglycoprotein receptor was isolated via immune precipitation from hepatoma Hep G2 cells following incubation with [32P]Pi. Analysis on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis revealed incorporation of 32P into both the 46 000 Da mature form of the receptor as well as the 40 000 Da precursor. The incorporated 32P was associated with phosphoserine. The degree of 32P incorporation was not substantially altered in cells endocytosing asialoglycoprotein ligand at maximal rates nor in cells in which receptor recycling was abolished by incubation with primaquine. That endocytosis and phosphorylation can be dissociated is supported by the observation that 32P is incorporated from [gamma-32P]ATP into the asialoglycoprotein receptor in isolated plasma membranes of Hep G2 cells.
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PMID:Phosphorylation of the human asialoglycoprotein receptor. 654 7

The lacto-N-neotetraose-containing lipooligosaccharide (LOS) present on the surface of most Neisseria gonorrhoeae organisms may serve many important functions in gonococcal pathogenesis. This surface glycolipid contains the cross-reactive epitope to human paragloboside and can be sialylated by gonococci grown in the presence of CMP-N-acetylneuraminic acid. Another possible role for this glycolipid could be to mimic human asialocarbohydrates and act as a ligand for asialoglycoprotein receptors contained on numerous human cells. The most noted of this large family of receptors is that expressed on the surface of hepatic cells. In a model cell system, using the hepatoma tissue culture cell line HepG2, we wanted to investigate if the presence of this asialoglycoprotein receptor influenced the adherence and/or invasion of gonococci expressing the lacto-N-neotetraose structure. Piliated variants of the gonococcal wild-type strain 1291 and its isogeneic LOS mutant 1291E were used in adherence-invasion assays. This gonococcal strain is somewhat unusual in that it expresses large amounts of predominantly one species of LOS, thus reducing the complexity of interpreting the data. The data from these assays suggested that the Gal(beta 1-4)GlcNAc(beta 1-3)Gal(beta 1-4)Glc carbohydrate structure on the wild-type LOS affected the adherence-invasion of gonococci into the HepG2 cells. In studies to determine whether the major hepatic asialoglycoprotein receptor was involved in these interactions, we found that the HepG2 cells contained two receptors which bound gonococcal LOS. One of these was the asialoglycoprotein receptor, and the data concerning this receptor will be reported elsewhere. The data on the second receptor are reported here. Purified, 125I-labeled gonococcal LOS was used to identify specific high-affinity LOS-binding sites. These binding experiments revealed one major binding site corresponding to a protein with a molecular mass of 70 kDa (p70). Several lines of evidence in this study suggested that the oligosaccharide region of LOS played an important role in LOS binding to the p70 of HepG2 cells. In addition, we show that this human LOS receptor has some similarities to the gonococcal Opa proteins.
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PMID:A lipooligosaccharide-binding site on HepG2 cells similar to the gonococcal opacity-associated surface protein Opa. 753 7

Receptor-mediated endocytosis was employed for a highly efficient transport of oligodeoxynucleotides into hepatoma cell line PLC/PRF/5. The oligodeoxynucleotides were bound to the asialofetuin-poly-L-lysine conjugate and this complex was internalized by the cells via asialoglycoprotein receptor, an endocytic receptor unique for hepatocytes. Binding of the oligodeoxynucleotides to the complex dramatically increased their cellular uptake more than 20-fold. Chloroquine, a lysosomatropic agent, further increased the transport of the complex but not of the free oligodeoxynucleotides.
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PMID:Receptor-mediated transport of oligodeoxynucleotides into hepatic cells. 768 60

99mTc-DTPA-galactosyl human serum albumin (99mTc-GSA) is a newly developed liver imaging ligand which specifically binds to asialoglycoprotein receptor on the hepatic cell surface. We investigated whether 99mTc-GSA scintigraphy was able to be used as indexes for the residual functional reserve and the early regeneration of the hepatocyte after the hepatic resection. Four patients with metastatic liver cancer, 3 patients with hepatocellular carcinoma, and 1 patient with cholangiocellular carcinoma were studied. Basically, each patient was examined 4 times (before, 3, 10, 20 days after the operation). Immediately after i.v. injection of 185 MBq (3 mg) of 99mTc-GSA, serial images and dynamic data were obtained. Serial changes of HH15, as an index of blood clearance of the tracer calculated from the uptake ratio of heart at 15 minutes to that at 3 minutes, and LHL15, as an index of hepatic accumulation calculated from the uptake ratio of liver to liver plus heart at 15 minutes after the injection were analyzed before and after hepatectomy. Three out of 4 lobectomy patients which showed increased HH15, and decreased LHL15 as compared with the preoperative data were considered to be decreased residual hepatic functional reserve. The remaining one lobectomy patient showed increased HH15, but increased LHL15 inversely. One patient of two partial resections of hepatocellular carcinoma with liver cirrhosis demonstrated transiently decreased HH15, and increased LHL15. Two patients with metastatic liver cancer (one partial resection, six partial resections) showed decreased HH15, and increased LHL15. Postoperatively increased hepatic accumulation was presumed to be increased functioning hepatocyte or transiently increased asialoglycoprotein receptor on the cell surface by up-regulation. 99mTc-GSA scintigraphy might be helpful for non-invasive method to detect the residual functional reserve and the early regeneration of the hepatocyte after the hepatic resection.
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PMID:[Evaluation of the residual functional reserve and the early regeneration after the hepatic resection using asialoglycoprotein receptor imaging agent]. 773 62

Optimal in vitro gene delivery with cationic lipids requires an excess of cationic charges with respect to DNA phosphates. In these conditions, in vivo delivery will be hampered by interference from cationic lipid-binding macromolecules either circulating or in the extracellular matrix. To overcome this problem, we are developing a modular transfection system based on lipid-coated DNA particles reminiscent of enveloped viruses. The particle core consists of the lipopolyamine-condensed nucleic acid in an electrically neutral ratio to which other synthetic lipids with key viral properties are hydrophobically adsorbed. As a first result, we have found that a good transfection level can be achieved simply with the neutral core particle, provided a zwitterionic lipid (dioleoyl phosphatidylethanolamine) is added to completely coat the DNA. Addition of lipids bearing a fusogenic or a nuclear localization peptide head group to the particles does not significantly improve an already efficient system, in contrast to polylysine-based gene transfer methods that rely on lysosomotropic or fusogenic agents to be effective. This emphasizes the distinctive properties of the lipopolyamines, including cell membrane destabilization, endosome buffering capacity, and possibly nuclear tropism. Most importantly, addition of lipids with a triantennary galactosyl residue drives the neutral nucleolipidic particles to the asialoglycoprotein receptor of human hepatoma HepG2 cells: Transfection increases approximately 1000-fold with 25% galactolipid. This receptor-mediated process is saturable and slightly less efficient than receptor-independent transfection obtained in vitro with a large excess of cationic lipid alone. Yet, electrically silent particles may provide an attractive solution for gene transfer in vivo where their external saccharide coat should allow them to diffuse within the organism and reach their target cells.
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PMID:Targeted gene transfer into hepatoma cells with lipopolyamine-condensed DNA particles presenting galactose ligands: a stage toward artificial viruses. 787 52


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