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)

Perhexiline is a lysosomotropic agent which has proved to be very valuable to certain patients suffering from angina pectoris. However long-term administration of the drug may induce hepato- and neuro-toxicity. Using HTC cells (a rat hepatoma-derived cell line) whose plasma membranes were labeled with NaB[3H]4 after oxidation by NaIO4, endocytosis and recycling of labeled asialo-orosomucoid (ASOR) receptors were investigated in the presence of 50 mumols/l perhexiline maleate. The results demonstrate that the drug induces a significant decrease of the rate of both the internalization and the recycling of ASOR receptors. The mechanisms responsible for these effects have not yet been elucidated. However, the current findings may be related to the previously observed inhibitory effect of perhexiline on cellular (Na+, K+)-ATPase and Mg++-ATPase activities. Our findings would then reflect insufficient cellular energy production, resulting from depressed ATP hydrolysis in the presence of perhexiline.
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PMID:Effects of perhexiline maleate on asialo-orosomucoid receptor endocytosis and recycling in HTC cells. 261

We describe a cell-free system for studying mitotic reorganization of nuclear structure. The system utilizes soluble extracts prepared from metaphase-arrested somatic chicken cells and supports both the disassembly and subsequent partial reassembly of exogenous nuclei. By fluorescence microscopy, biochemical fractionation, protein phosphorylation assays and electron microscopy, we show that chicken embryonic nuclei incubated in extracts prepared from metaphase-arrested chicken hepatoma cells undergo nuclear envelope breakdown, lamina depolymerization and chromatin condensation. These prophase-like events are strictly dependent on ATP and do not occur when nuclei are incubated in interphase extracts. Compared to interphase extracts, metaphase extracts show increased kinase activities toward a number of nuclear protein substrates, including lamins and histone H1; moreover, they specifically contain four soluble phosphoproteins of Mr 38,000, 75,000, 95,000 and 165,000. Following disassembly of exogenous nuclei in metaphase extracts, telophase-like reassembly of a nuclear lamina and re-formation of nuclear membranes around condensed chromatin can be induced by depletion of ATP from the extract. We anticipate that this reversible cell-free system will contribute to the identification and characterization of factors involved in regulatory and mechanistic aspects of mitosis.
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PMID:A somatic cell-derived system for studying both early and late mitotic events in vitro. 263 78

The degradation of endogenous adenine nucleotides was compared in mitochondria isolated from mouse and rat liver, rat renal cortex and solid hepatoma. Mitochondria were incubated for 30 min at 37 degrees C in the presence of carboxyatractyloside and oligomycin. In rat liver mitochondria ATP, ADP and AMP were degraded by about 25% each, whereas in kidney and hepatoma mitochondria a rapid decline of ATP and ADP but no change in the AMP contents were observed. Main products formed were adenosine, inosine and hypoxanthine in all mitochondria examined. Compartment studies revealed that the main route of intramitochondrial adenine nucleotide catabolism seems to proceed via AMP dephosphorylation and subsequent adenosine deamination.
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PMID:The adenine nucleotide catabolism in nonphosphorylating mitochondria of different tissues. 273 Jun 29

Cycloheximide injection of rats results in the activation of a protein kinase that phosphorylates 40 S ribosomal protein S6. This Ca2+/cyclic nucleotide-independent kinase exhibits chromatographic properties that are indistinguishable from the S6 kinase in H4 hepatoma cells whose activity is stimulated by insulin and growth factors and the S6 kinase that is activated during liver regeneration. The enzyme has been purified 50,000-fold to near homogeneity: a critical step in purification employs a peptide affinity column using a synthetic peptide corresponding to the carboxyl-terminal 32-amino acid residues of mouse liver S6, which encompasses all S6 phosphorylation sites. The purified enzyme is a 70,000-dalton polypeptide that is reactive with azido-ATP. In addition to 40 S ribosomal S6 and the synthetic peptide, the S6 kinase catalyzes rapid phosphorylation of a number of other protein substrates including histone H2b, glycogen synthase, and ATP citrate lyase; this last protein is phosphorylated by S6 kinase in vitro on the same serine residue that is phosphorylated in response to insulin and epidermal growth factor in intact hepatocytes. Moreover, the S6 kinase catalyzes the phosphorylation of a number of hepatic nonhistone nuclear proteins. This S6 kinase probably underlies the increased hepatic S6 phosphorylation observed after cycloheximide treatment, which in turn corresponds to the mitogen-activated S6 kinase.
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PMID:Purification of a hepatic S6 kinase from cycloheximide-treated Rats. 276 46

N6,N6-Dibenzoyl-2',3'-O-isopropylideneadenosine, which is readily synthesized by one-pot 5'-O-trimethylsilylation, N6-benzoylation, and desilylation, was converted to the corresponding 5'-aldehyde. This was treated with CH2 = CHMgBr to afford, after debenzoylation, a 1:3 mixture of the 5'S and 5'R epimers, respectively, of 5'-C-vinyl-2',3'-O-isopropylideneadenosine. The configurations were established by single-crystal X-ray diffraction analysis of the 5'R epimer. Hydroboration of the 5'-O-tetrahydropyranyl derivative of the mixed epimeric 5'-C-vinyl nucleosides readily furnished 5'(S,R)-C-(2-hydroxyethyl)-2',3'-O-isopropylideneadenosine. Treatment of the 5'(S,R)-C-(2-O-tosyl) derivative of this with disodium L-homocysteinate permitted facile introduction of the L-ethionine system. By means of methods developed earlier in the synthesis of homologous methionine-ATP adducts, the alpha-amino acid group was protected, a beta,gamma-imidotriphosphoryl group was introduced at O5', and blocking groups were removed to give the title adduct as a 2:3 mixture of its two 5' epimers. It was a powerful inhibitor [KM(ATP)/Ki = 520 and 340] of the M-2 (normal tissue) and M-T (hepatoma tissue) forms, respectively, of the title enzyme and displayed predominantly competitive kinetics with the two substrates L-methionine and MgATP. It inhibited M-2 and M-T slightly less effectively than its homologue possessing one less CH2 between sulfur and C5' and gave kinetic evidence of an increased tendency to form L-methionine-enzyme-adduct and MgATP-enzyme-adduct complexes.
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PMID:Approaches to isozyme-specific inhibitors. 16. A novel methyl-C5' covalent adduct of L-ethionine and beta,gamma-imido-ATP as a potent multisubstrate inhibitor of rat methionine adenosyltransferases. 278 35

The malate-aspartate shuttle activity for the reoxidation of cytosolic NADH was studied in MC29 avian hepatoma cells whose mitochondria preferentially utilized glutamine and produced aspartate for ATP formation. The tumour cells showed reoxidation of NADH, as evidenced by the accumulation of pyruvate, when incubated aerobically with L-lactate. The involvement of the respiratory chain and transaminase in the process was demonstrated by the addition of specific inhibitors. When the tumour cells were cultured in Eagle's medium with aminooxyacetate or in the absence of glutamine, a marked reduction in the cellular NAD/NADH ratio was observed. These results indicate that the malate-aspartate shuttle was actively functioning in the tumour cells and that this hepatoma may provide a suitable system for the investigation of the bioenergetics of malignant cells.
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PMID:Oxidation of cytosolic NADH by the malate-aspartate shuttle in MC29 hepatoma cells. 280 84

The requirement for ATP hydrolysis in the initiation of RNA polymerase II (Pol II)-directed transcription and the relationship between ATP and novobiocin action led us to investigate whether novobiocin could inhibit transcription of the mouse metallothionein-I (MT-I) gene. Novobiocin inhibited the MT-I gene transcription in a fractionated rat hepatoma nuclear extract in a dose-dependent manner by direct interaction with a nuclear factor(s). This interaction prevented formation of stable preinitiation complexes but did not affect elongation of MT-I mRNA. Preincubation of the nuclear extract with ATP prevented the action of novobiocin on MT-I gene transcription. Although novobiocin is known to inhibit DNA topoisomerase II, VM-26, a specific inhibitor of this enzyme had no effect on the transcription. These results indicate that novobiocin blocks the Pol II-directed transcription by inhibiting formation of preinitiation complexes at an ATP-dependent step.
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PMID:Novobiocin inhibits initiation of RNA polymerase II-directed transcription of the mouse metallothionein-I gene independent of its effect on DNA topoisomerase II. 282 31

H-35 rat hepatoma cells were labelled with [32P]orthophosphate and their insulin receptors isolated on wheat germ agglutinin (WGA)-agarose and anti-(insulin receptor) serum. The incubation of these cells with 10 mM-H2O2 for 10 min increased the phosphorylation of both the serine and tyrosine residues of the beta subunit of the insulin receptor. Next, insulin receptors were purified on WGA-agarose from control and H2O2-treated H-35 cells and the purified fractions incubated with [gamma-32P]ATP and Mn2+. Phosphorylation of the beta subunit of insulin receptors obtained from H2O2-treated cells was 150% of that of control cells. The kinase activity of the WGA-purified receptor preparation obtained from H2O2-treated cells, as measured by phosphorylation of src-related synthetic peptide, was increased about 4-fold over control cells. These data suggest that in intact cell systems, H2O2 may increase the insulin receptor kinase activity by inducing phosphorylation of the beta subunit of insulin receptor.
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PMID:Hydrogen peroxide stimulates tyrosine phosphorylation of the insulin receptor and its tyrosine kinase activity in intact cells. 283 39

A human hepatoma cell line (Li-7A) possesses ectoATPase activity which is activated by either Mg2+ or Ca2+. Both ectoMg2+-ATPase and ectoCa2+-ATPase hydrolyze other nucleoside triphosphates, are inactive with ADP and AMP, and are inhibited by both p-chloromercuriphenyl sulfonate (pCMPS) and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. Different Km values for ATP and pH curves are obtained for ectoMg2+-ATPase and ectoCa2+-ATPase. The specific activities of the two ATPases remain relatively constant through several days of cell growth after an initial decrease. In contrast, the specific activities of the two ATPases, especially the ectoCa2+-ATPase, increases continuously in Li-7A cells cultured in the presence of EGF, cholera toxin, and hydrocortisone. The ATPases of the factor-treated cells are also indiscriminate with respect to nucleoside triphosphate substrates; however, the kinetic constants for substrates are altered when compared to that of the untreated cells. Most strikingly, the sensitivity to inhibitors is greatly reduced. It is concluded that the long-term effect of EGF, cholera toxin, and hydrocortisone on the Li-7A cells is the induction or activation of a new or minor component of the ectoATPases, which is preferentially activated by Ca2+ and insensitive to pCMPS.
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PMID:Differential expression of ectoMg2+-ATPase and ectoCa2+-ATPase activities in human hepatoma cells. 283 48

Ubiquitin, a 76 amino acid protein, is covalently attached to abnormal and short-lived proteins, thus marking them for ATP-dependent proteolysis in eukaryotic cells. Free (unconjugated) ubiquitin was localized in hepatoma cells using affinity purified anti-ubiquitin antibodies and colloidal gold immunoelectron microscopy. The anti-ubiquitin antibodies recognize only unconjugated ubiquitin. Ubiquitin is found within the cytoplasm, nucleus, the microvilli, autophagic vacuoles and lysosomes.
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PMID:Immunoelectron microscopic localization of ubiquitin in hepatoma cells. 284 72


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