Roles of insulin receptor substrate-1 and Shc on insulin-like growth factor I receptor signaling in early passages of cultured human fibroblasts.
Insulin-like growth factor-I (IGF-I) improves glucose metabolism and growth in patients with leprechaunism. We investigated signal transduction through IGF-I receptor in comparison with epidermal growth factor (EGF) receptor in early passages of cultured skin fibroblasts from a normal subject and a patient with leprechaunism whose insulin receptor tyrosine kinase was almost nonexistent. Insulin receptor substrate-1 (IRS-1) became tyrosine-phosphorylated and bound growth factor receptor-bound protein 2 (GRB2) quickly by IGF-I. The association of Shc with GRB2 by IGF-I was detected by immunoblot with anti-Shc antibody but was hardly visible with antiphosphotyrosine antibody, which was in marked contrast to efficient tyrosine phosphorylation of Shc by EGF. However, the potency of IGF-I for DNA synthesis was far stronger than EGF, which was not parallel with the potency of these growth factors to activate Shc or MAP kinase. Rather, phosphatidylinositol (PI) 3-kinase activity, which was activated by IGF-I about 5- to 10-fold more strongly than EGF, appeared to correlate with mitogenesis. Signal transduction pathways following IGF-I receptor or EGF receptor activation were indistinguishable between the normal subject and the patient. Our results strongly suggest that in human skin fibroblasts, which represent a more physiological cell culture: 1) IRS-1, rather than Shc, is the major tyrosine-phosphorylated protein binding GRB2 in initial phase of IGF-I signaling; 2) mitogenic potency of receptor tyrosine kinases such as IGF-I receptor and EGF receptor may not be determined solely by the amount of Shc-GRB2 complex or the activity of MAP kinase; and 3) in contrast to previous reports, IGF-I and EGF receptor signalings are not defective in leprechaunism.
Takahashi
Y
Y
Institute for Diabetes Care and Research, Asahi Life Foundation, Tokyo, Japan.
Tobe
K
K
Kadowaki
H
H
Katsumata
D
D
Fukushima
Y
Y
Yazaki
Y
Y
Akanuma
Y
Y
Kadowaki
T
T
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002455:Cell Division; D002478:Cells, Cultured; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D007163:Immunosorbent Techniques; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology; D008934:Mitogens / Q000494:pharmacology; D009154:Mutation; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; C526292:IRS1 protein, human; D055504:Insulin Receptor Substrate Proteins; D008934:Mitogens; D010750:Phosphoproteins; D011506:Proteins; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D016222:Fibroblast Growth Factor 2; D019000:Phosphotyrosine; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin; D017871:Calcium-Calmodulin-Dependent Protein Kinases