Giorgetti S, Pelicci P G, Pelicci G, Van Obberghen E
Institut National de la Santé et de la Recherche Médicale U 145, Faculté de Médecine, Nice, France.
Eur J Biochem. 1994 Jul 1;223(1):195-202. doi: 10.1111/j.1432-1033.1994.tb18983.x.
Src homology/collagen (SHC) proteins are thought to participate in signaling through both receptor tyrosine kinases, such as the insulin receptor and the EGF (epidermal growth factor) receptor, and cytoplasmic tyrosine kinases, such as v-src and v-fps. Here we approached the insulin-induced and the insulin-like-growth-factor-I-induced (IGF-I-induced) phosphorylation of SHC proteins, and the possible role of these proteins in insulin and IGF-I signaling. First, we showed that SHC proteins are phosphorylated on tyrosine residues upon insulin and IGF-I treatment of fibroblasts transfected with a SHC cDNA construct. More important, ligand-activated insulin and IGF-I receptors phosphorylate SHC proteins in vitro, indicating that SHC proteins could be direct substrates for insulin and IGF-I receptors. Further, insulin or IGF-I treatment of SHC-transfected fibroblasts leads to immunoprecipitation of SHC proteins with insulin-receptor substrate 1 (IRS-1). We next looked at the possible effect of SHC proteins on biological responses in SHC-transfected fibroblasts. We found that the expression of exogenous SHC proteins results in an increased basal MEK (MAPK/ERK-activating kinase) activity. Further, neither the basal nor the insulin-induced or IGF-I-induced PtdIns-3-kinase activity were modified by expression of exogenous SHC proteins. These results illustrate that SHC proteins are implicated in the MAP (mitogen-activated protein)-kinase pathway, but not in that of PtdIns-3-kinase. Finally, we show that SHC-transfected cells, unlike control cells, are able to advance into the early phases of the cell cycle, and are more sensitive to the growth-promoting effect of insulin. In conclusion, SHC proteins are substrates for insulin and IGF-I receptors, and would appear to function as early post-receptor signaling components.
Src同源/胶原蛋白（SHC）蛋白被认为通过受体酪氨酸激酶（如胰岛素受体和表皮生长因子（EGF）受体）以及细胞质酪氨酸激酶（如v-src和v-fps）参与信号传导。在此，我们研究了胰岛素诱导的和胰岛素样生长因子-I诱导的（IGF-I诱导的）SHC蛋白磷酸化，以及这些蛋白在胰岛素和IGF-I信号传导中的可能作用。首先，我们发现用SHC cDNA构建体转染的成纤维细胞经胰岛素和IGF-I处理后，SHC蛋白的酪氨酸残基会发生磷酸化。更重要的是，配体激活的胰岛素和IGF-I受体在体外可使SHC蛋白磷酸化，这表明SHC蛋白可能是胰岛素和IGF-I受体的直接底物。此外，对转染SHC的成纤维细胞进行胰岛素或IGF-I处理会导致SHC蛋白与胰岛素受体底物1（IRS-1）发生免疫沉淀。接下来，我们研究了SHC蛋白对转染SHC的成纤维细胞生物学反应的可能影响。我们发现外源性SHC蛋白的表达会导致基础MEK（丝裂原活化蛋白激酶/细胞外信号调节激酶激活激酶）活性增加。此外，外源性SHC蛋白的表达并未改变基础的、胰岛素诱导的或IGF-I诱导的磷脂酰肌醇-3激酶活性。这些结果表明，SHC蛋白参与丝裂原活化蛋白（MAP）激酶途径，但不参与磷脂酰肌醇-3激酶途径。最后，我们发现与对照细胞不同，转染SHC的细胞能够进入细胞周期的早期阶段，并且对胰岛素的促生长作用更敏感。总之，SHC蛋白是胰岛素和IGF-I受体的底物，似乎作为受体后早期信号成分发挥作用。
