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)

Insulin stimulated autophosphorylation of the beta-subunit of the insulin receptor purified from Fao hepatoma cells or purified from Chinese hamster ovary (CHO/HIRC) or Swiss 3T3 (3T3/HIRC) cells transfected with the wild-type human insulin receptor cDNA. Autophosphorylation of the purified receptor occurred in at least two regions of the beta-subunit: the regulatory region containing Tyr-1146, Tyr-1150, and Tyr-1151, and the C-terminus containing Tyr-1316 and Tyr-1322. In the presence of antiphosphotyrosine antibody (alpha-PY), autophosphorylation of the purified receptor was inhibited nearly 80% during insulin stimulation. Tryptic peptide mapping showed that alpha-PY inhibited autophosphorylation of both tyrosyl residues in the C-terminus and one tyrosyl residue in the regulatory region, either Tyr-1150 or Tyr-1151. Thus, a bis-phosphorylated form of the regulatory region accumulated in the presence of alpha-PY, which contained Tyr(P)-1146 and either Tyr(P)-1150 or 1151. In intact Fao, CHO/HIRC, and 3T3/HIRC cells, insulin stimulated tyrosyl phosphorylation of the beta-subunit of the insulin receptor. Tryptic peptide mapping indicated that the regulatory region of the beta-subunit was mainly (greater than 80%) bis-phosphorylated; however, all three tyrosyl residues of the regulatory region were phosphorylated in about 20% of the receptors. As the phosphotransferase was activated by tris-phosphorylation but not bis-phosphorylation of the regulatory region of the beta-subunit (White et al.: Journal of Biological Chemistry 263:2969-2980, 1988), the extent of autophosphorylation in the regulatory region may play an important regulatory role during signal transmission in the intact cell.
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PMID:Cascade of autophosphorylation in the beta-subunit of the insulin receptor. 272 71

Amino acid sequence of the precursor of the phosphorylated N-glycoprotein (pp63) secreted by rat hepatocytes was deduced from the cDNA sequence. This polypeptide (Mr = 40,586) was rich in both cysteine and proline and contained three potential N-glycosylation sites. A single pp63 mRNA species (approximately 2000 bp), found in normal hepatocytes but not in FaO hepatoma cells, appeared to result from transcription of a single gene. pp63 purified by affinity chromatography inhibited insulin receptor tyrosine kinase and receptor autophosphorylation. Only the phosphorylated form of the protein was active. In additon, pp63 antagonized the growth-promoting action of insulin in FaO cells but did not affect hormone-mediated increase in amino acid transport capacity or tyrosine aminotransferase induction in these cells.
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PMID:Characterization of a natural inhibitor of the insulin receptor tyrosine kinase: cDNA cloning, purification, and anti-mitogenic activity. 276 55

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

The receptors for insulin and insulin-like growth factor I (IGF-I) are closely related molecules, with an extracellular binding domain and an intracellular tyrosine kinase domain. The interaction of insulin and IGF-I with their respective receptors activates the receptor kinase domain, leading to the biological actions of the hormones. Since insulin generally regulates metabolic events and IGF-I generally regulates growth events, it is believed that structural differences in the tyrosine kinase domains of the two respective receptors may elicit different biological responses via different transmembrane signaling mechanisms. We studied the regulation of glycogen metabolism and amino acid uptake in human cultured HEP-G2 hepatoma cells, which have distinct receptors for both insulin and IGF-I. The receptor specificity of these responses was probed with specific monoclonal antibodies to both the insulin and IGF-I receptors. Stimulation of both [3H]glucose incorporation into glycogen and alpha-[3H]aminoisobutyric acid uptake by insulin was half-maximal at concentrations of 1-5 nmol/L. These effects were blocked by the insulin receptor monoclonal antibody MA-10, but not by the IGF-I receptor antibody alpha IR-3. Stimulation of both functions by IGF-I was half-maximal at concentrations of 1-5 nmol/L, and these effects were inhibited by alpha IR-3, but not by MA-10. These studies indicate that in HEP-G2 cells both insulin and IGF-I, via their own receptors, stimulate the same biological responses.
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PMID:Insulin and insulin-like growth factor I regulate the same biological functions in HEP-G2 cells via their own specific receptors. 283 99

The ability of insulin and an insulinomimetic oligosaccharide (IOS) isolated from conditioned medium of Reuber hepatoma cells to regulate protein phosphorylation in 3T3-L1 adipocytes and Fao hepatoma cells has been examined in extracts prepared from 32P-labeled cells and by immunoblotting of unlabeled extracts with an anti-phosphotyrosine antibody. In 32P-labeled 3T3-L1 cells, both insulin and IOS stimulate the dephosphorylation of a 55K membrane-associated protein, yet only insulin stimulates the phosphorylation of the ribosomal S6 protein and a 22K heat-stable soluble protein. In 32P-labeled Fao cells, both insulin and IOS stimulate the phosphorylation of a 16K protein, but only insulin stimulates S6 phosphorylation. As judged by immunoblotting, IOS does not stimulate the tyrosine phosphorylation of the beta subunit of the insulin receptor and a 180K soluble protein in a manner similar to insulin. These data indicate that the insulinomimetic effects of IOS are selective for certain insulin-regulated pathways and that the effects of IOS are unlikely to be operating through stimulation of the insulin receptor tyrosine kinase.
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PMID:Regulation of protein phosphorylation by insulin and an insulinomimetic oligosaccharide in 3T3-L1 adipocytes and Fao hepatoma cells. 283 76

Two H4IIE hepatoma cell genes, phosphoenolpyruvate carboxykinase (PEPCK) and gene 33 (g33), are reciprocally regulated by insulin. Quantitation of mRNAPEPCK and mRNAg33 in total RNA isolated from cells treated with insulin showed a 7-fold increase in mRNAg33 amount and a 3-fold decrease of mRNAPEPCK. The cAMP analog 8-(4-chlorophenylthio)-cAMP induced mRNAPEPCK but had no effect on mRNAg33. The responses to various insulins and related molecules showed that the insulin receptor mediates the effects of physiologic concentrations of insulin on each of these genes. This inverse pattern of regulation by insulin was further characterized by determining the transcription rates of both genes in nuclei isolated at various times after the addition of insulin and 8-(4-chlorophenylthio)-cAMP to H4IIE cells. Insulin increased the rate of synthesis of mRNAg33 from 35 to 354 ppm and decreased the synthesis of mRNAPEPCK from 1175 to 109 ppm. These effects of insulin occurred rapidly and reached their maxima by 60 min. In both cases, greater effects were observed as insulin concentrations were increased from 10(-12) to 10(-8) M. Although the effects of insulin were concentration-dependent for both genes, the PEPCK gene was significantly more sensitive to low concentrations of insulin than was gene 33. The reciprocal effects of insulin on the synthesis of mRNAPEPCK and mRNAg33 in H4IIE cells provide a means of investigating how a hormone can exert opposing effects on two genes in the same cell.
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PMID:Reciprocal regulation of gene transcription by insulin. Inhibition of the phosphoenolpyruvate carboxykinase gene and stimulation of gene 33 in a single cell type. 284 5

We have studied the biosynthesis of the insulin receptor in a human hepatoma cell line, HepG2. As previously reported, these cells synthesize a disulphide-bonded alpha 2 beta 2 tetrameric insulin receptor. Labelling of HepG2 cells with [3H]palmitate or [3H]myristate followed by immunoprecipitation with a polyclonal antireceptor antibody revealed the incorporation of palmitate, but not myristate, into the beta-subunit and alpha beta-precursor of the receptor in a hydroxylamine-sensitive linkage. The extracellular alpha-subunit was not labelled, demonstrating the specificity of incorporation. Acylation of the insulin receptor was an early event as judged by fatty acid incorporation into the alpha beta-precursor and prevention by protein synthesis inhibitors. Pulse-chase studies demonstrated the expected processing of the alpha beta-precursor to mature alpha- and beta-subunits, but no evidence for preferential turnover of the fatty acid moiety was found. The site of acylation appears to be in the transmembrane or cytoplasmic domain since proteolytic treatment of intact cells produced a truncated beta-subunit still containing label. Binding studies showed that HepG2 cells contain approximately half as many insulin-like growth factor-1 receptors as insulin receptors, raising the possibility that this receptor may also be acylated. Indeed, immunoprecipitation with the antiinsulin receptor serum of MDCK cells expressing IGF-1 receptors, but not insulin receptors, revealed bands corresponding to the alpha beta-precursor, alpha- and beta-subunits, of which the alpha beta-precursor and beta-subunits incorporated [3H]palmitate but the alpha-subunit did not.
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PMID:Insulin and IGF-1 receptors contain covalently bound palmitic acid. 284 52

We have previously reported that insulin induces a complete and reversible desensitization to the induction of tyrosine aminotransferase by insulin and insulin-like growth factors (IGFs) in HTC rat hepatoma cells. This loss of responsiveness cannot be accounted for by down-regulation of cell surface receptors, but occurs at a postbinding step in hormone action. Here we present evidence that IGF-I and IGF-II also induce desensitization to the actions of both IGFs and insulin and that this effect is mediated by IGF receptors. First, the concentration dependence for this effect is similar to that for the IGF-I and IGF-II induction of tyrosine aminotransferase, which has been shown to be mediated by IGF receptors. Second, antibody to the insulin receptor, which blocks insulin, but not IGF-II, binding to HTC cells, causes a rightward shift in the concentration dependence for insulin induction of desensitization, but does not significantly change the concentration dependence for IGF-II. These results indicate that IGF-II-induced desensitization to IGF-II is not mediated by the insulin receptor, but presumably by an IGF receptor. Although the IGFs do cause a moderate decrease in the binding of IGFs and insulin (to approximately 50-75% of the control value), this cannot account for the virtually complete desensitization to their actions. We conclude that IGFs, like insulin, induce a nearly complete loss of responsiveness to insulin and IGFs, that this effect is mediated via IGF receptors, and that desensitization occurs at a step distal to hormone binding which may be common to the actions of insulin and the IGFs.
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PMID:Regulation of insulin and insulin-like growth factor (IGF) responsiveness by IGFs in rat hepatoma cells. 287 Sep 17

The rat hepatoma H35 cells in serum-free medium produce tyrosine aminotransferase (TAT) and initiate DNA synthesis and cell division upon exposure to 10(-9)-10(-10) M insulin. This insulin-dependent hormonal and mitogenic stimulation is through the insulin receptors and not through the receptors for insulin-like growth factor type I. We have isolated genetic variants of H35 cells which are resistant to a cytotoxic insulin-diphtheria toxin A fragment conjugate. These variants showed different degrees of insulin binding capacity and exhibited different sensitivities to insulin-stimulated TAT and DNA synthesis. Variant DTaI-b had a slight decrease in number of insulin receptors but completely lost sensitivity to both TAT and DNA stimulation. Variant 11-1 had a reduced number of insulin receptors but retained both TAT and DNA inducibilities. Variant 14-1, which had a high number of insulin receptors, was not responsive to DNA synthesis but was responsive to TAT induction. The beta-subunit of insulin receptors in these cell variants had different sensitivities to their insulin-dependent autophosphorylation. The rat hepatoma HTC cells used as a control showed very low insulin binding, no stimulation of TAT and DNA synthesis by insulin, and no detectable insulin-enhancement of beta-subunit phosphorylation. These characteristics provide genetic evidence for the divergence of the insulin receptor-mediated mitogenic and hormonal signals during the post-receptor pathways which is apparently regulated by the insulin-dependent phosphorylation.
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PMID:Rat hepatoma cell variants resistant to insulin-diphtheria toxin A fragment conjugates. Genetic evidence for the separate pathways for insulin receptor-mediated mitogenic and hormonal stimulation. 287 15

We have used H-35 rat hepatoma cells to test whether the type II insulin-like growth factor (IGF) receptor mediates metabolic responses to IGF-II. On the basis of both affinity cross-linking experiments and competition binding experiments, H-35 cells display insulin and type II IGF receptors, but not type I IGF receptors. IGF-II and multiplication-stimulating activity (MSA; the rat homolog of IGF-II) stimulate tyrosine aminotransferase, amino acid transport, and glycogen synthase activities to the same magnitude as insulin. However, MSA and IGF-II stimulate these metabolic responses only at high concentrations, indicating that these peptides are acting through the insulin receptor. Incubation of H-35 cells with MSA also induces a state of unresponsiveness to the further actions of both MSA and insulin. There is no associated loss of either insulin or IGF-II binding, indicating that desensitization occurs at a postbinding step in hormone action. The high concentration of MSA necessary to induce desensitization is also consistent with MSA acting through the insulin receptor. We conclude that in H-35 cells, the insulin receptor, rather than the type II IGF receptor, mediates the metabolic responses stimulated by MSA and IGF-II as well as the MSA-induced desensitization to insulin and MSA action.
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PMID:Mediation of insulin-like growth factor actions by the insulin receptor in H-35 rat hepatoma cells. 287 66


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