Richards R G, Walker M P, Sebastian J, DiAugustine R P
Hormones and Cancer Group, Laboratory of Molecular Carcinogenesis, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
J Biol Chem. 1998 May 8;273(19):11962-9. doi: 10.1074/jbc.273.19.11962.
Some of the actions of estradiol occur through stimulation of growth factor pathways in target organs. Tyrosine-phosphorylated (Tyr(P)) insulin-like growth factor-1 receptor (IGF-1R) and the insulin receptor substrate (IRS)-1 are found in the uterus of mice treated with estradiol. Immunoprecipitates of uterine Tyr(P) IRS-1 contained both p85, the regulatory subunit of phosphatidylinositol (PI) 3-kinase, and PI 3-kinase catalytic activity. Estradiol also stimulated binding of IRS-1 and PI 3-kinase to the IGF-1R. Depletion of IRS-1 from uterine extracts reduced PI 3-kinase associated with the receptor, which suggests that binding of the enzyme to IGF-1R occurs primarily in a complex that also contains IRS-1. Following treatment with estradiol, formation of Tyr(P) IGF-1R, Tyr(P) IRS-1, and the p85.IRS-1 complex was very weak in the uterus of IGF-1(m/m) mice, which are severely deficient in IGF-1. This indicated that most, if not all, of the estradiol-stimulated Tyr phosphorylation of uterine IRS-1 originates from ligand activation of IGF-1R kinase. IRS-2 was also Tyr-phosphorylated in the normal uterus and bound more IGF-1R and p85 in response to estradiol; however, a marked decrease in levels of uterine IRS-2 occurred 12-24 h after treatment with estradiol. Since IRS-2 was present in IGF-1R precipitates and a recombinant form of IGF-1 (long R3 IGF-1) stimulated formation of Tyr(P) IRS-2, hormonal activation of this docking protein probably occurs through the IGF-1R. In summary, our findings show that estrogen activation of uterine IGF-1R kinase results in enhanced binding of p85 (PI 3-kinase) to IRS-1 and IRS-2. The formation of one or both of these complexes may be important for the potent mitogenic action of this steroid. That estradiol stimulated a decrease of IRS-2, but not of IRS-1, suggests that these docking proteins have different roles in hormone-induced signaling in the uterus.
雌二醇的一些作用是通过刺激靶器官中的生长因子信号通路来实现的。在用雌二醇处理的小鼠子宫中发现了酪氨酸磷酸化（Tyr(P)）的胰岛素样生长因子-1受体（IGF-1R）和胰岛素受体底物（IRS）-1。子宫Tyr(P) IRS-1的免疫沉淀物中既含有磷脂酰肌醇（PI）3激酶的调节亚基p85，也含有PI 3激酶的催化活性。雌二醇还刺激了IRS-1和PI 3激酶与IGF-1R的结合。从子宫提取物中去除IRS-1会减少与受体相关的PI 3激酶，这表明该酶与IGF-1R的结合主要发生在一个也包含IRS-1的复合物中。在用雌二醇处理后，在严重缺乏IGF-1的IGF-1(m/m)小鼠子宫中，Tyr(P) IGF-1R、Tyr(P) IRS-1和p85.IRS-1复合物的形成非常微弱。这表明，子宫IRS-1中大部分（如果不是全部）由雌二醇刺激的酪氨酸磷酸化源自IGF-1R激酶的配体激活。在正常子宫中，IRS-2也发生酪氨酸磷酸化，并在雌二醇作用下与更多的IGF-1R和p85结合；然而，在用雌二醇处理12 - 24小时后，子宫IRS-2水平显著下降。由于IRS-2存在于IGF-1R沉淀物中，并且重组形式的IGF-1（长R3 IGF-1）刺激了Tyr(P) IRS-2的形成，这种对接蛋白的激素激活可能通过IGF-1R发生。总之，我们的研究结果表明，子宫IGF-1R激酶的雌激素激活导致p85（PI 3激酶）与IRS-1和IRS-2的结合增强。这些复合物中一种或两种的形成可能对这种类固醇的强大促有丝分裂作用很重要。雌二醇刺激了IRS-2而非IRS-1的减少，这表明这些对接蛋白在子宫激素诱导的信号传导中具有不同的作用。
