UMLS:C0019204 - FACTA Search

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Query: UMLS:C0019204 (hepatocellular carcinoma)
71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of the insulin receptor tyrosine kinase (protein-tyrosine kinase, EC 2.7.1.112) in various rapid insulin effects was studied by injecting four different cell types (by osmotic lysis of pinocytotic vesicles) with a monoclonal antibody that specifically inhibits the kinase activity of the insulin receptor and the closely related receptor for insulin-like growth factor (IGF)-I. Injection of this inhibitory antibody resulted in a decreased ability of insulin to stimulate the uptake of 2-deoxyglucose in Chinese hamster ovary cells and freshly isolated rat adipocytes, ribosomal protein S6 phosphorylation in CHO cells, and glycogen synthesis in the human hepatoma cell line HepG2. The ability of insulin, IGF-I, and IGF-II to stimulate glucose uptake in TA1 mouse adipocytes was also inhibited. Studies with CHO cells demonstrated that these effects of the inhibitory antibody were specific, since there was no change in phorbol ester-stimulated glucose uptake and injection of a noninhibiting antibody to the kinase had no effect on insulin action. These studies indicate that the tyrosine kinase activity of the insulin receptor is important in mediating several rapid insulin effects in a variety of different cell types.
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PMID:Acute insulin action requires insulin receptor kinase activity: introduction of an inhibitory monoclonal antibody into mammalian cells blocks the rapid effects of insulin. 354 Sep 58

The receptors for insulin and epidermal growth factor possess tyrosine-specific protein kinase activity which may play a role in mediating the biological actions of these two peptides. We have identified a 120 kDa glycoprotein (pp120) in rat liver plasma membranes which can be phosphorylated by the insulin receptor in a cell-free system and in intact cultured hepatoma cells. In the present report, we have demonstrated in a cell-free system that solubilized epidermal growth factor receptors can phosphorylate tyrosine residues in pp120.
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PMID:Rat liver membranes contain a 120 kDa glycoprotein which serves as a substrate for the tyrosine kinases of the receptors for insulin and epidermal growth factor. 354 68

Insulin has pleiotropic effects on sensitive cells, including the regulation of specific mRNA accumulation initiated by the binding of insulin to its plasma membrane receptor. Lectins, such as wheat germ agglutinin (WGA) and concanavalin A (Con A), are known to be insulin mimetic. It is thought that WGA and Con A interact with the insulin receptor or associated membrane glycoproteins which, when activated, lead to insulin-mimetic responses. We attempted to determine whether WGA and Con A could induce the accumulation of a specific messenger RNA (p33-mRNA). Insulin treatment of H4IIE (H4) hepatoma cells increased the concentration of p33-mRNA within 30 min after addition, with a maximum effect of 10- to 15-fold. WGA and Con A also exhibited time- and dose-dependent stimulatory effects on p33-mRNA accumulation with maximal effects of 30- to 40-fold. The effect of insulin was maximal by 1 h and plateaued thereafter, whereas lectins had maximal effects at 2 h after addition to cell cultures. Insulin, WGA, and Con A did not significantly alter the stability (half-life) of p33-mRNA. The addition of RNA synthesis inhibitors blocked the ability of insulin, WGA, and Con A to induce the amount of p33-mRNA. These data suggest that lectins, as well as insulin, induce the synthesis of p33-mRNA in acutely treated H4 hepatoma cells.
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PMID:Insulin-mimetic actions of wheat germ agglutinin and concanavalin A on specific mRNA levels. 355 40

We investigated the biosynthesis of the human insulin receptor in IM-9 lymphocytes and HEP-G2 hepatoma cells. Cells were first pulse labeled for 15 min with [35S]methionine and then chased for up to 4 h. At each time, the cells were solubilized in 1% Triton X-100; the insulin receptor was immunoprecipitated and then analyzed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (6%) and fluorography. At 15 min, a major precursor protein of 190,000 Mr was precipitated. During the chase period, two smaller proteins became apparent, which evolved into two major species of 130,000 and 95,000 Mr, the mature alpha- and beta-subunits, respectively. When IM-9 cells were trypsinized after pulse chase, the alpha- and beta-subunits were completely digested, whereas the 190,000-Mr precursor was unaffected. 125I-surface labeling of cells, followed by immunoprecipitation, revealed the presence of only the alpha- and beta-subunits, indicating that only these two species were on the cell surface. To study this biosynthetic pathway, several inhibitors were used (tunicamycin, monensin, and swainsonine). These inhibitors revealed the following. The receptor is first synthesized as a 170,000-Mr protein that is cotranslationally N-glycosylated to yield a high-mannose 190,000-Mr precursor. This precursor is rapidly transported from the endoplasmic reticulum to the Golgi apparatus where it is cleaved into two subunits of 120,000 Mr (alpha) and 90,000 Mr (beta). These subunits then increase in molecular weight by processing of the high-mannose oligosaccharides to the low-mannose complex type. The two subunits then migrate to the cell surface where they function to transmit the insulin signal.
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PMID:Biosynthesis and processing of the human insulin receptor. 372 Oct 67

Six sulphonylureas (tolbutamide, tolazamide, chlorpropamide, glibornuride, glipizide and gliquidone) and 2 biguanides (metformin and buformin) were tested for possible effects on insulin binding to H 35 rat hepatoma cells in culture. Insulin binding was measured after 24 and 72 hr of culturing cells in medium containing the drugs. Buformin and gliquidone were tested in concentrations from 10(-8)-5 X 10(-5) M, the other drugs in concentrations from 10(-7)-5 X 10(-4) M. All 24-hr experiments were repeated in cells down-regulated with 10 micrograms/ml insulin. None of the oral hypoglycemic agents tested had any significant influence on insulin binding to H 35 hepatoma cells, either in the presence or absence of insulin. We suggest that the insulin receptor status, at least in this type of liver cell, is not influenced by sulphonylureas or biguanides.
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PMID:Sulphonylureas and biguanides do not affect insulin binding in H35 hepatoma cells. 375 14

Phosphorylation of the insulin receptor was studied in intact well differentiated hepatoma cells (Fao) and in a solubilized and partially purified receptor preparation obtained from these cells by affinity chromatography on wheat germ agglutinin agarose. Tryptic peptides containing the phosphorylation sites of the beta-subunit of the insulin receptor were analyzed by reverse-phase high performance liquid chromatography. Phosphoamino acid content of these peptides was determined by acid hydrolysis and high voltage electrophoresis. Separation of the phosphopeptides from unstimulated Fao cells revealed one major and two minor phosphoserine-containing peptides and a single minor phosphothreonine-containing peptide. Insulin (10(-7) M) increased the phosphorylation of the beta-subunit of the insulin receptor 3- to 4-fold in the intact Fao cell. After insulin stimulation, two phosphotyrosine-containing peptides were identified. Tyrosine phosphorylation reached a steady state within 20 s after the addition of insulin and remained nearly constant for 1 h. Under our experimental conditions, no significant change in the amount of [32P]phosphoserine or [32P]phosphothreonine associated with the beta-subunit was found during the initial response of cells to insulin. When the insulin receptor was extracted from the Fao cells and incubated in vitro with [gamma-32P]ATP and Mn2+, very little phosphorylation occurred in the absence of insulin. In this preparation, insulin rapidly stimulated autophosphorylation of the receptor on tyrosine residues only and high performance liquid chromatography analysis of the beta-subunit digested with trypsin revealed one minor and two major phosphopeptides. The elution position of the minor peptide corresponded to that of the major phosphotyrosine-containing peptide obtained from the beta-subunit of the insulin-stimulated receptor labeled in vivo. In contrast, the elution position of one of the major phosphopeptides that occurred during in vitro phosphorylation corresponded to the minor phosphotyrosine-containing peptide phosphorylated in vivo. The other major in vitro phosphotyrosine-containing peptide was not detected in vivo. Our results indicate that: tyrosine phosphorylation of the insulin receptor occurs rapidly following insulin binding to intact cells; the level of tyrosine phosphorylation remains constant for up to 1 h; the specificity of the receptor kinase or accessibility of the phosphorylation sites are different in vivo and in vitro.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Differences in the sites of phosphorylation of the insulin receptor in vivo and in vitro. 384 33

The phosphorylation characteristics of insulin receptor from control and insulin-treated rat H-35 hepatoma cells 32P-labeled to equilibrium have been documented. The 32P-labeled insulin receptor is isolated by immunoprecipitation with patient-derived insulin receptor antibodies in the presence of phosphatase and protease inhibitors to preserve the native phosphorylation and structural characteristics of the receptor. The unstimulated insulin receptor contains predominantly [32P] phosphoserine and trace amounts of [32P]phosphothreonine in its beta subunit. In response to insulin, the insulin receptor beta subunit exhibits marked tyrosine phosphorylation and a 2-fold increase in total [32P]phosphoserine contents. High pressure liquid chromatography of the tryptic hydrolysates of the 32P-labeled receptor beta subunit from quiescent cells results in the resolution of up to 9 fractions containing [32P]phosphoserine. The insulin-stimulated tyrosine phosphorylation is concentrated in two of these receptor phosphopeptide fractions, whereas the increase in [32P]phosphoserine content is scattered in low abundance over all receptor tryptic fractions. Insulin receptors affinity-purified by lectin- and insulin-agarose chromatographies from insulin-treated, 32P-labeled cells exhibit a 22-fold increase in the Vmax of receptor tyrosine kinase activity toward histone when compared to controls. The elevated kinase activity of the insulin receptor derived from insulin-treated cells is not due to the presence of hormone bound to the receptor because the receptor kinase activity is assayed while immobilized on insulin-agarose. Furthermore, the insulin-activated receptor kinase activity is reversed following dephosphorylation of the receptor beta subunit with alkaline phosphatase in vitro. The correlation between the insulin-stimulated site specific tyrosine phosphorylation on receptor beta subunit and the elevation of receptor tyrosine kinase activity strongly suggests that the insulin receptor kinase is activated by hormone-stimulated autophosphorylation on tyrosine residues in intact cells, as previously demonstrated for the purified receptor.
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PMID:Tyrosine phosphorylation of insulin receptor beta subunit activates the receptor tyrosine kinase in intact H-35 hepatoma cells. 395 14

We have studied the reversibility of insulin receptor phosphorylation to establish the relation between this autophosphorylation reaction and the initiation of insulin action and between dephosphorylation and the termination of insulin effects in cells. In cultured Fao hepatoma cells labeled with 32PO4(3-), insulin increased 5-fold the phosphorylation of the beta-subunit of the insulin receptor at serine, threonine, and tyrosine residues. Addition of anti-insulin antiserum to cells incubated with insulin caused dissociation of insulin from the receptor and concurrent dephosphorylation of the beta-subunit. 32PO4(3-) associated with the insulin-stimulated receptor could be decreased by the addition of sodium phosphate to the medium but with a slower time course. Insulin stimulated phosphorylation of insulin receptor purified partially on immobilized wheat germ agglutinin. This reaction utilized [gamma-32P] ATP and occurred exclusively on tyrosine residues. Addition of unlabeled ATP caused a decrease in the amount of PO4(3-) associated with the receptor. Insulin-stimulated phosphorylation was also observed if the receptors were further purified by immunoprecipitation with anti-insulin receptor antibody prior to the phosphorylation reaction; however, addition of unlabeled ATP to this system did not chase the labeled 32PO4(3-) from the beta-subunit. These data are consistent with the notion that phosphorylation and dephosphorylation of the insulin receptor parallel the onset and termination of insulin action. Phosphatase activity involved in the dephosphorylation of the insulin receptor appears to be a glycoprotein because it was retained after partial purification of the receptor on wheat germ agglutinin-agarose; however, this phosphatase activity is distinct from the insulin receptor because it was not retained after immunoprecipitation of the receptor with anti-insulin receptor antibodies.
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PMID:Phosphorylation and dephosphorylation of the insulin receptor: evidence against an intrinsic phosphatase activity. 608 92

Insulin and the insulinlike growth factors (IGF-I and IGF-II) are members of a family of hormones that regulate the metabolism and growth of many tissues. Cultured HEP-G2 cells (a minimal deviation human hepatoma) have insulin receptors and respond to insulin by increasing their glycogen metabolism. In the present study with HEP-G2 cells, we used 125I-labeled insulin, IGF-I, and IGF-II to identify distinct receptors for each hormone by competition-inhibition studies. Unlabeled insulin was able to inhibit 125I-IGF-I binding but not 125I-IGF-II binding. A mouse monoclonal antibody to the human insulin receptor that inhibits insulin binding and blocks insulin action inhibited 75% of 125I-insulin binding, but inhibited neither 125I-IGF-I nor 125I-IGF-II binding. When glycogen metabolism was studied, insulin stimulated [3H]glucose incorporation into glycogen in a biphasic manner; one phase that was 20-30% of the maximal response occurred over 1-100 pM, and the other phase occurred over 100 pM-100 nM. The anti-receptor monoclonal antibody inhibited the first phase of insulin stimulation but not the second. Both IGF-I and IGF-II stimulated [3H]glucose incorporation over the range of 10 pM-10 nM; IGF-I was three to fivefold more potent. The monoclonal antibody, however, was without effect on IGF regulation of glycogen metabolism. Therefore, these studies indicate that insulin as well as the IGFs at physiological concentrations regulate glycogen metabolism in HEP-G2 cells. Moreover, this regulation of glycogen metabolism is mediated by both the insulin receptor and the IGF receptors.
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PMID:Dual regulation of glycogen metabolism by insulin and insulin-like growth factors in human hepatoma cells (HEP-G2). Analysis with an anti-receptor monoclonal antibody. 609 May 2

The immunoglobulin fraction prepared from the serum of a rabbit immunized with purified type II insulin-like growth factor (IGF) receptor from rat placenta was tested for its specificity in inhibiting receptor binding of 125I-IGF II and for its ability to modulate IGF II action on rat hepatoma H-35 cells. The specific binding of 125I-IGF II to plasma membrane preparations from several rat cell types and tissues was inhibited by the anti-IGF II receptor Ig. Affinity cross-linking of 125I-IGF II to the Mr = 250,000 type II IGF receptor structure in rat liver membranes was blocked by the anti-receptor Ig, while no effect on affinity labeling of insulin receptor with 125I-insulin or IGF I receptor with 125I-IGF I or 125I-IGF II was observed. The specific inhibition of ligand binding to the IGF II receptor by anti-receptor Ig was species-specific such that mouse receptor was less potently inhibited and human receptor was unaffected. Rat hepatoma H-35 cells contain insulin and IGF II receptor, but not IGF I receptor, and respond half-maximally to insulin at 10(-10) M and to IGF II at higher concentrations with increased cell proliferation (Massague, J., Blinderman, L.A., and Czech, M.P. (1982) J. Biol. Chem. 257, 13958-13963). Addition of anti-IGF II receptor Ig to intact H-35 cells inhibited the specific binding of 125I-IGF II to the cells by 70-90%, but had no detectable effect on 125I-insulin binding. Significantly, under identical conditions anti-IGF II receptor Ig was without effect on IGF II action on DNA synthesis at both submaximal and maximal concentrations of IGF II. This finding and the higher concentrations of IGF II required for growth promotion in comparison to insulin strongly suggest that the Mr = 250,000 receptor structure for IGF II is not involved in mediating this physiological response. Rather, at least in H-35 cells, the insulin receptor appears to mediate the effects of IGF II on cell growth. Consistent with this interpretation, anti-insulin receptor Ig but not anti-IGF II receptor Ig mimicked the ability of growth factors to stimulate DNA synthesis in H-35 cells. We conclude that the IGF II receptor may not play a role in transmembrane signaling, but rather serves some other physiological function.
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PMID:The type II insulin-like growth factor receptor does not mediate increased DNA synthesis in H-35 hepatoma cells. 609 44

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