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  • fibroblasts  (1)
  • insolin action  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Mechanisms of insulin resistance in cultured fibroblasts from a patient with leprechaunism: resistance to proteolytic activation of glycogen synthase by trypsin (1985)
    Springer
    Molecular and cellular biochemistry 66 (1985), S. 117-125 
    Details
    ISSN: 1573-4919
    Keywords: fibroblasts ; glycogen synthase ; insulin resistance ; trypsin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary Post-receptor or post-binding events in the action of insulin have been investigated in cultured skin fibroblasts from an infant with leprechaunism. Both diminished binding of insulin and multiplication-stimulating activity (MSA) to these cells as well as deficits distal to binding were described in a previous publication. Exposure of control fibroblasts to low concentrations (0.001 to 0.01%) of trypsin for one min without glucose in the medium activated the enzyme glycogen synthase; activation was less than that observed with a maximally effective concentration (10−6 M) of insulin alone. In cells from the patient with leprechaunism, the effect of trypsin was much smaller than in the control fibroblasts. Exposing the control cells to soybean trypsin inhibitor before addition of trypsin prevented activation of glycogen synthase and demonstrated the specificity of the proteolytic action of trypsin. The rates of activation and inactivation of glycogen synthase in vitro were similar in extracts of the control subject's and the patient's fibroblasts and indicated that the enzymes regulating the phosphorylation/ dephosphorylation of glycogen synthase were intact in the patient's cells. Total glycogen synthase activity and glycogen content were also indistinguishable in control and leprechaun fibroblasts. These results are compatible with the presence of an abnormality in the structure or availability of the protease substrate from which chemical mediators of insulin action are formed in the patient's cells. Two possible models for a receptor-coupling complex are proposed. Either a mutation in a regulator-substrate unit of the receptor-coupling complexes for insulin and certain insulin-like growth factors or an alteration in the environment of the unit are postulated to explain the findings. Established Investigator of the American Diabetes Association.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220779
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  • 2
    Electronic Resource
    Electronic Resource
    Inhibition of insulin receptor phosphorylation by indomethacin (1985)
    Springer
    Molecular and cellular biochemistry 69 (1985), S. 83-90 
    Details
    ISSN: 1573-4919
    Keywords: Insulin receptor ; phosphorylation ; indomethacin ; insolin action
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Insulin stimulated phosphorylation of tyrosine residues by the insulin receptor kinase may be part of a signalling mechanism associated with insulin's action. We report that indomethacin inhibited the phosphorylation of the β-subunit of the solubilized adipocyte insulin receptor. Indomethacin also inhibited several insulin-sensitive processes in intact rat adipocytes. Indomethacin (1 mM) inhibited basal phosphorylation of the β-subunit of the solubilized insulin receptor by 6007o and insulin-stimulated phosphorylation by 30%. In adipocytes, indomethacin inhibited basal 3-0-[methyl-14C]-methyl-D glucose transport by 50070 (P 〈 0.01), D-[6-14C]-glucose oxidation by 5007o (P 〈 0.01), D-[6-14C]-glucose conversion to lipid by 30010 (P 〈 0.01), and D-[1-14C]-glucose conversion to lipid by 6007o (P〈0.01). Similarly, indomethacin inhibited insulin-stimulated 3-0-[methyl-14C]-methyl-D-glucose transport by 75070 (P〈0.01), D-[6-14C]-glucose oxidation by 20% (P〈0.05), D-[1-14C]-glucose oxidation by 35070 (P〈0.01), D-[6-14C] glucose conversion to lipid by 25010 (P〈0.01), and D-[1-14C] glucose conversion to lipid by 4501o (P〈0.01). In contrast, insulin binding to its receptor, basal D-[1-14C]-glucose oxidation and both basal and insulin-stimulated activation of glycogen synthase were unaffected by indomethacin. Thus, indomethacin partially inhibited autophosphorylation of the solubilized insulin receptor on tyrosine and partially inhibited some but not all of insulin's actions. This supports the hypothesis that insulin's metabolic effects are linked to activation of the insulin receptor protein kinase and indicates that there may be heterogeneity in the mechanisms of intracellular metabolic control by insulin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225930
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    Paper (German National Licenses)
    Fulltext
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