Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.1.1.17 (ornithine decarboxylase)
 6,351 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human insulin-like growth factor I and II (IGF-I and IGF-II) in concentrations of 1-30 ng/ml, were shown to stimulate ornithine decarboxylase activity and [3H]thymidine incorporation in human SH-SY5Y neuroblastoma cells. Proliferation of these cells was also stimulated by IGF-I and II when added to RPMI 1640 medium, fortified with selenium, hydrocortisone, transferrin, and beta-estradiol. Labeled IGF-I and II bound to SH-SY5Y cells. The cross-reaction pattern of IGF-I, IGF-II, and insulin in competing with the binding of labeled IGF-I and IGF-II, respectively, indicated that SH-SY5Y cells express both type I and type II IGF receptors. Treatment of SH-SY5Y cells for 4 d with 12-O-tetradecanoylphorbol-13-acetate (TPA), which resulted in morphological and functional differentiation and growth inhibition, abolished the mitogenic response to both IGF-I and II. Concomitantly, the binding of IGF-II disappeared almost totally, which offers a possible explanation for the reduced biological response to IGF-II after TPA treatment. In contrast, the IGF-I binding in TPA-treated cells was only reduced to approximately 70% of the binding to control cells. It is therefore not excluded that the IGF-I receptor could be uncoupled by TPA, with persistent binding capacity for IGF-I.
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PMID:Mitogenic response of human SH-SY5Y neuroblastoma cells to insulin-like growth factor I and II is dependent on the stage of differentiation. 300 92

The insulin and insulin-like growth factor-I (IGF-I) receptors are related heterotetramers consisting of two extracellular ligand-binding alpha-subunits and two transmembrane beta-subunits whose cytoplasmic domains exhibit tyrosine kinase activity. Previous studies have shown that ATP binding by the cytoplasmic tyrosine kinase domains of these receptors is necessary to initiate the signal transduction pathway triggered by ligands or by ligand-mimetic antibodies, suggesting that receptor autophosphorylation is a necessary proximal step in this pathway. In the case of the insulin receptor, it has additionally been demonstrated that a cluster of three tyrosines in the kinase domain itself are the first to be phosphorylated, and that autophosphorylation of these particular residues is necessary for receptor activity. Using stably transfected NIH-3T3 cell lines, we now show that mutation of the analogous residues in the IGF-I receptor abolishes all short, intermediate, and long-term responses to IGF-I. These data suggest that the initial mechanisms of activation of the insulin and IGF-I receptors are very similar. Additionally, we have identified two parameters, induction of c-fos gene expression and ornithine decarboxylase enzyme activity, which are extremely sensitive to IGF-I stimulation and which will be particularly useful in evaluating the biological activity of other mutated versions of the IGF-I receptor.
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PMID:Essential role of tyrosine residues 1131, 1135, and 1136 of the insulin-like growth factor-I (IGF-I) receptor in IGF-I action. 751 94

The insulin-like growth factor-I (IGF-I) receptor is a member of a large family of transmembrane signal transducing molecules. The defining characteristic of this class of receptors is the intrinsic tyrosine kinase activity of the cytoplasmic domain. While it has been demonstrated that this tyrosine kinase activity is necessary for the action of a number of transmembrane tyrosine kinase receptors, no evidence of this type has been adduced to date with respect to the signaling requirement of the IGF-I receptor. We have now shown that stably transfected NIH-3T3 cell lines overexpressing human IGF-I receptors display increased responses to IGF-I and an IGF-I-mimetic antibody, alpha IR-3, in terms of short, intermediate, and long term actions initiated by activation of the IGF-I receptor. These include receptor autophosphorylation, activation of phosphatidylinositol-3-kinase and 2-deoxyglucose uptake, induction of ornithine decarboxylase gene expression, and stimulation of thymidine incorporation. In short term responses, the kinetics seen with alpha IR-3 were slower than those seen with IGF-I. These effects were severely decreased in clones expressing human IGF-I receptors in which the lysine residue in the ATP-binding site of the tyrosine kinase domain had been mutated to alanine or arginine. This was true for both IGF-I and alpha IR-3. These results indicate that, for all parameters tested, the tyrosine kinase activity of the IGF-I receptor is necessary for activation of the IGF-I-stimulated signal transduction cascade. Additionally, the effects of alpha IR-3 also require tyrosine kinase activity.
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PMID:Role of tyrosine kinase activity in signal transduction by the insulin-like growth factor-I (IGF-I) receptor. Characterization of kinase-deficient IGF-I receptors and the action of an IGF-I-mimetic antibody (alpha IR-3). 767 99