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  • 1
    Electronic Resource
    Electronic Resource
    Persistent infection with a nontransforming RNA virus leads to impaired growth factor receptors and response (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 128 (1986), S. 457-465 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The potential role of viral persistence with nontransforming viruses on cellular growth and cellular function has received little attention. We found that when infected with type 3 reovirus (five plaque-forming units (PFU)/cell), balb/C 3T3 cells (a mouse embryo fibroblast cell line) undergo a limited lytic phase. The surviving cells, about 90% of the original cells, appear morphologically normal by light microscopy and exhibit normal growth patterns in serum-supplemented medium but are persistently infected by electron microscopy. These persistently infected cells shed infectious virus in the culture medium (1.6-60 × 106 PFU per 106 cells per 24 h). In comparison to control uninfected 3T3 cells, the persistently infected cells exhibit a 70-90% decrease in receptor number for epidermal growth factor (EGF). This occurs without production of any EGF-like material and is associated with a parallel decrease in EGF-stimulated DNA synthesis. By contrast, insulin receptors are increased in number three-fold and insulin and serum stimulated DNA synthesis are comparable to control uninfected cells. These results suggest that persistent infection with a nontransforming virus may lead to major alteration in control of cell growth by specific growth factors.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041280315
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  • 2
    Electronic Resource
    Electronic Resource
    Augmented desensitization to epidermal growth factor (EGF) immediate actions: A novel mechanism for altered EGF growth response in mutant A431 cells (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 142 (1990), S. 231-235 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Epidermal growth factor (EGF) may either stimulate or inhibit cell growth. To elucidate the mechanism of these varied effects, we compared EGF action in parental A431 cells in which cell growth is inhibited, and clone 15, a mutant of these cells resistant to EGF growth inhibition. In both lines, EGF receptor was present in similar concentrations and underwent tyrosine phosphorylation to the same extent. Likewise, in both lines, acute exposure to EGF stimulated an increase in free cytoplasmic [Ca2+], as well as a similar increase in phosphoryla-tion of lipocortin 1, a major substrate for the EGF receptor kinase whose phos-phorylation is calcium-dependent. On the other hand, pretreatment of clone 15 cells with EGF for 72 h abolished EGF-induced phosphorylation of lipocortin 1 and led to a loss of the increase in cytoplasmic free [Ca2+], whereas no such desensitization was seen in the parental A431 cells. These data indicate a link between EGF-induced increase in cytoplasmic calcium, lipocortin phosphoryla-tion, and cell growth and suggest that differences in mechanisms of desensitization to these immediate actions of EGF may lead to altered growth response to this hormone.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041420203
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  • 3
    Electronic Resource
    Electronic Resource
    Phosphorylation of the solubilized insulin receptor by the gene product of the Rous sarcoma virus, pp60src (1984)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 26 (1984), S. 169-179 
    Details
    ISSN: 0730-2312
    Keywords: insulin receptor ; tyrosine kinase ; pp60src ; phosphorylation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Both the insulin receptor and the gene product of the Rous sarcoma virus, pp60src, are protein kinases which phosphorylate themselves and other proteins on tyrosinc residues. Addition of the solubilized insulin receptor to purified pp60src increased the phosphorylation of the β-subunit of the insulin receptor. Phosphorylation of the insulin receptor by pp60src occurred both in the absence and presence of insulin but did not alter the insulin dose response for autophosphorylation of the receptor. Increasing concentrations of pp60src increased the phosphorylation of the receptor and at high concentrations equaled the maximal effect produced by insulin. Our observations suggest a possible mechanism by which the metabolically regulated insulin receptor tyrosine kinase could be altered by other tyrosine kinases such as that associated with pp60src. Further studies will be required to determine if the insulin receptor is phosphorylated by pp60src in Rous sarcoma virus-infected cells.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240260305
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  • 4
    Electronic Resource
    Electronic Resource
    Interaction of the insulin receptor kinase with serine/threonine kinases in vitro (1985)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 28 (1985), S. 171-182 
    Details
    ISSN: 0730-2312
    Keywords: insulin receptor ; tyrosine phosphorylation ; serine kinases ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Insulin causes rapid phosphorylation of the β subunit (Mr = 95,000) of its receptor in broken cell preparations. This occurs on tyrosine residues and is due to activation of a protein kinase which is contained in the receptor itself. In the intact cell, insulin also stimulates the phosphorylation of the receptor and other cellular proteins on serine and threonine residues. In an attempt to find a protein that might link the receptor tyrosine kinase to these serine/threonine phosphorylation reactions, we have studied the interaction of a partially purified preparation of insulin receptor with purified preparations of serine/threoine kinases known to phosphorylate glycogen synthase. No insulin-dependent phosphorylation was ob served when casein kinases I and II, phosphorylase kinase, or glycogen synthase kinase 3 was incubated in vitro with the insulin receptor. These kinases also failed to phosphorylate the receptor. By contrast, the insulin receptor kinase catalyzed the phosphorylation of the calmodulin-dependent kinase and addition of insulin in vitro resulted in a 40% increase in this phosphorylation. In the presence of calmodulin-dependent kinase and the insulin receptor kinase, insulin also stimulated the phosphorylation of calmodulin. Phosphoamino acid analysis showed an increase of phosphotyrosine content in both calmodulin and calmodulindependent protein kinase. These data suggest that the insulin receptor kinase may interact directly and specifically with the calmodulin-dependent kinase and calmodulin. Further studies will be required to determine if these phosphorylations modify the action of these regulatory proteins.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240280209
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  • 5
    Electronic Resource
    Electronic Resource
    Phosphorylation of glycolytic and gluconeogenic enzymes by the insulin receptor kinase (1987)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 33 (1987), S. 15-26 
    Details
    ISSN: 0730-2312
    Keywords: phosphorylation ; insulin receptor ; tyrosine kinase ; phosphofructokinase ; glycolysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Various glycolytic and gluconeogenic enzymes were tested as substrates for the insulin receptor kinase. Phosphofructokinase and phosphoglycerate mutase were found to be the best substrates. Phosphorylation of these enzymes was rapid, stimulated 2- to 6-fold by 10-7 M insulin and occurred exclusively on tyrosine residues. Enolase, fructose 1,6-bisphosphatase, lactate dehydrogenases in decreasing order, were also subject to insulin-stimulated phosphorylation but to a smaller extent than that for phpsphofructokinase or phosphoglycerate mutase.The phosphorylation of phosphofructokinase was studied most extensively since phosphofructokinase is known to catalyze a rate-limiting step in glycolosis. The apparent Km of the insulin receptor for phosphofructokinase was 0.1 μM, which is within the physiologic range of concentration of this enzyme in most cells. Tyrosine phosphorylation of phosphofructokinase paralleled autophosphorylation of the β-subunit of the insulin receptor with respect to time course, insulin dose response (half maximal effect between 10-9 and 10-8 M insulin), and cation requirement (Mn2+ 〉 Mg2+ 〉 〉 Ca2+). Further study will be required to determine whether the tyrosine phosphorylation of phosphofructokinase plays a role in insulin-stimulated increases in glycolytic flux.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240330103
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  • 6
    Electronic Resource
    Electronic Resource
    Cascade of autophosphorylation in the β-subunit of the insulin receptor (1989)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 39 (1989), S. 429-441 
    Details
    ISSN: 0730-2312
    Keywords: transmembrane signal ; protein phosphorylation ; tyrosine kinase ; signal transmission ; phosphorylation cascade ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Insulin stimulated autophosphorylation of the β-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 β-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 (α-PY), autophosphorylation of the purified receptor was inhibited nearly 80% during insulin stimulation. Tryptic peptide mapping showed that α-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 α-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 β-subunit of the insulin receptor. Tryptic peptide mapping indicated that the regulatory region of the β-subunit was mainly (〉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 β-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.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240390409
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  • 7
    Electronic Resource
    Electronic Resource
    Insulin induces rapid accumulation of insulin receptors and increases tyrosine kinase activity in the nucleus of cultured adipocytes (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 157 (1993), S. 217-228 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To better understand the mechanism by which insulin exerts effects on events at the cell nucleus, we have studied insulin receptors and tyrosine kinase activity in nuclei isolated by sucrose density gradient centrifugation following insulin treatment of differentiated 3T3-F442A cells. Insulin stimulated nuclear accumulation of insulin receptors by approximately threefold at 5 min. The half-maximal effect was observed with 1-10 nM insulin. Following insulin treatment, phosphotyrosine content associated with the nuclear insulin receptor was also increased by twofold at 5 min with a similar insulin concentration dependency. These nuclear insulin receptors differ from the membrane-associated insulin receptors in that they were not efficiently solubilized with 1% Triton X-100. During the same period of time, insulin stimulaced nuclear tyrosine kinase activity toward the exogenous substrate poly Glu4: Tyr1 tenfold in a time-dependent manner reaching a maximum at 30 min. The insulin receptor substrate protein 1 (IRS-1) could not be detected in the nucleus by immunoblotting. However, a nuclear protein with Mr ≈ 220 kDa was tyrosine phosphorylated, and insulin further stimulated this process threefold 〉30 mins. Surface labeling was performed to determine if the nuclear insulin receptors would emerge from the plasma membrane fraction. Using 1251-BPA-insulin with intact cells, the intensity of nuclear insulin receptor labeling was negligible and not increased throughout 30 min incubation at 37°C. In contrast, there was an increase in labeled receptors in the microsomal fraction following insulin treatment. Taken together, these results indicate that insulin rapidly increases nuclear insulin receptor appearance and activates nuclear tyrosine kinase activity. The insulin-induced accumulation of nuclear insulin receptors cannot be accounted for by internalization of surface membrane receptors. These effects of insulin may play an important role in action of the hormone at the nuclear level. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041570203
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  • 8
    Electronic Resource
    Electronic Resource
    Quantitative dissociation between EGF effects on c-myc and c-fos gene expression, DNA synthesis, and epidermal growth factor receptor tyrosine kinase activity (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 150 (1992), S. 180-187 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The exact relationship between EGF-stimulated tyrosine phosphorylation, induction of the cellular proto-oncogenes c-myc and c-fos, and DNA synthesis remains uncertain. Madin-Darby Canine Kidney (MDCK) cells possess EGF receptor sites with high binding capacity, and in contrast to A431 cells, respond to EGF by increasing DNA synthesis. Following EGF stimulation of intact MDCK cells, there was a rapid and marked increase in the autophosphorylation of the EGF receptor. This was associated with an increase in the tyrosine phosphorylation of a 120 kDa phosphoprotein believed to be an endogenous substrate of this receptor kinase. The ED50 for stimulation of phosphorylation of pp120 was -0.05 nM versus 1.0 nM for receptor autophosphorylation, consistent with amplification of signalling at this step in EGF action. Stimulation of DNA synthesis occurred after 12 to 24 hours and revealed even further amplification with an ED50 of about 0.1 nM. Intermediate between these events was a time-dependent activation of c-fos and c-myc gene expression. However, the ED50 for these processes was ã10 nM, indicating a relatively lower sensitivity of EGF for stimulation of proto-oncogene expression. Tyrphostin (RG 50864), a compound reported to inhibit specifically the EGF receptor kinase, completely blocked EGF stimulation of proto-oncogene induction. Interestingly, under the same experimental conditions, EGF receptor autophosphorylation was decreased only 60%. These data, along with the dose-response studies, indicate that proto-oncogene induction requires near maximal stimulation of EGF receptor autophosphorylation. They also suggest that, in MDCK cells, the EGF dependent induction of the c-fos and c-myc genes is not strictly correlated to the extent of EGF receptor autophosphorylation or EGF-stimulated DNA synthesis, and that EGF stimulation of DNA synthesis likely involves additional rate-limiting intermediate steps.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041500124
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  • 9
    Electronic Resource
    Electronic Resource
    Modulation of expression of insulin and IGF-I receptor by Epstein-Barr virus and its gene products LMP and EBNA-2 in lymphocyte cell lines (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 154 (1993), S. 486-495 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The receptors for insulin and insulin-like growth factor I (IGF-I) are two closely related integral membrane glycoproteins involved in signalling of cell growth and metabolism. We have used the unique paradigm of pairs of Burkitt lymphoma cell lines (BLO2, BL30, BL41) with or without Epstein-Barr Virus (EBV) infection and cells transfected with EBV-related genes to examine effects of EBV on expression of these receptors at the gene and protein functional level. In BL30 and BL41 cells, EBV infection increased surface insulin binding and total receptor number by 2-and 18-fold, respectively. By contrast, EBV infection decreased total IGF-I receptors by 29 to 87% in all three cell lines. In general, there was a correlation between total receptor concentration and the level of insulin or IGF-I receptor mRNAs, although in one cell line insulin binding increased while receptor mRNA levels decreased slightly, suggesting posttranslational effects. BL41 cells transfected with a vector expressing the EBV latent membrane protein (LMP) exhibited a 2.6- to 3.2-fold increase in insulin receptor expression, whereas cells transfected with EBNA-2 (one of the EBV nuclear antigens) alone exhibited no effect. However, EBNA-2 appears to be required for the EBV effect on insulin receptor expression since cells infected with a mutant virus, P3JHRI, which lacks the EBNA-2 gene failed to show an increase in insulin receptor number. These data indicate that EBV infection of lymphocytes increases expression of insulin receptors while simultaneously decreasing expression of IGF-I receptors. The magnitude and sometimes even the direction of change, depends on host cell factors. A maximal increase in insulin receptors appears to require the coordinate action of several of the EBV proteins including LMP and EBNA-2. © 1993 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041540306
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