Yamamoto K, Lapetina E G, Moxham C P
Division of Cell Biology, Burroughs Wellcome Co., Research Triangle Park, North Carolina 27709.
Endocrinology. 1992 Mar;130(3):1490-8. doi: 10.1210/endo.130.3.1311242.
Stimulation by insulin-like growth factor-I (IGF-I) of LISN C4 cells, a mouse fibroblast cell line that overexpresses human IGF-I receptors, led to an increase in the amount of a phosphatidylinositol kinase that could be immunoprecipitated by anti-IGF-I receptor or anti-phosphotyrosine antibodies. The identity of the lipid produced in phosphatidylinositol kinase assays of anti-IGF-I receptor or anti-phosphotyrosine immunoprecipitates indicated that IGF-I selectively increased the amount of immunoprecipitated phosphatidylinositol 3-kinase activity. The amount of immunoprecipitated phosphatidylinositol 3-kinase activity that was increased by IGF-I followed a time course that paralleled the stimulation of IGF-I receptor beta-subunit autophosphorylation. The amount of phosphatidylinositol 3-kinase activity detected in anti-IGF-I receptor immunoprecipitates represented only 2% of that which was immunoprecipitated by anti-phosphotyrosine antibody. Furthermore, phosphatidylinositol 3-kinase activity which was recovered with anti-phosphotyrosine antibody was present in both cytosol and particulate cell fractions at approximately similar levels. Taken together, these results suggest that the stimulation of the IGF-I receptor tyrosine kinase leads to an increase in the amount of phosphatidyl inositol 3-kinase activity immunoprecipitated by antiphosphotyrosine and anti-IGF-I receptor antibodies and to a limited association with the IGF-I receptor itself, even though these cells express very high levels of IGF-I receptors. That the majority of phosphatidylinositol 3-kinase activity does not tightly associate with the IGF-I receptor after IGF-I stimulation suggests that it may be associated with other tyrosine phosphorylated proteins. Alternatively, the kinase itself may become phosphorylated on tyrosine and dissociate from the IGF-I receptor. In this manner, an increase of phosphatidylinositol 3-kinase activity by IGF-I deviates from the activation of phosphatidylinositol 3-kinase by platelet-derived growth factor receptor in that a tight association with the receptor is not produced after stimulation.
胰岛素样生长因子-I（IGF-I）对LISN C4细胞（一种过表达人IGF-I受体的小鼠成纤维细胞系）的刺激，导致一种磷脂酰肌醇激酶的量增加，该激酶可被抗IGF-I受体或抗磷酸酪氨酸抗体免疫沉淀。抗IGF-I受体或抗磷酸酪氨酸免疫沉淀物的磷脂酰肌醇激酶测定中产生的脂质的身份表明，IGF-I选择性地增加了免疫沉淀的磷脂酰肌醇3-激酶活性的量。IGF-I增加的免疫沉淀的磷脂酰肌醇3-激酶活性的量遵循与IGF-I受体β亚基自磷酸化刺激平行的时间进程。在抗IGF-I受体免疫沉淀物中检测到的磷脂酰肌醇3-激酶活性的量仅占抗磷酸酪氨酸抗体免疫沉淀量的2%。此外，用抗磷酸酪氨酸抗体回收的磷脂酰肌醇3-激酶活性在胞质溶胶和颗粒细胞组分中以大致相似的水平存在。综上所述，这些结果表明，IGF-I受体酪氨酸激酶的刺激导致抗磷酸酪氨酸和抗IGF-I受体抗体免疫沉淀的磷脂酰肌醇3-激酶活性的量增加，并且与IGF-I受体本身的结合有限，尽管这些细胞表达非常高水平的IGF-I受体。IGF-I刺激后，大多数磷脂酰肌醇3-激酶活性不与IGF-I受体紧密结合，这表明它可能与其他酪氨酸磷酸化蛋白相关。或者，激酶本身可能在酪氨酸上磷酸化并从IGF-I受体解离。以这种方式，IGF-I对磷脂酰肌醇3-激酶活性的增加与血小板衍生生长因子受体对磷脂酰肌醇3-激酶的激活不同，因为刺激后不会与受体产生紧密结合。
