Kuhné M R, Pawson T, Lienhard G E, Feng G S
Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755.
J Biol Chem. 1993 Jun 5;268(16):11479-81.
The insulin receptor substrate 1 (IRS1) is a protein that is rapidly phosphorylated on tyrosine by the activated insulin receptor. Syp is a recently discovered, broadly expressed phosphotyrosine (Tyr(P)) phosphatase that contains two Src homology 2 (SH2) domains. We have found that insulin treatment of 3T3-L1 adipocytes leads to complex formation between IRS1 and Syp. Syp was detected in immunoadsorbates of IRS1 from extracts of insulin-treated but not basal cells by both immunoblotting and Tyr(P) phosphatase activity. The association of Syp with IRS1 apparently occurs between the SH2 domains of Syp and Tyr(P)-containing sequences of IRS1, since a fusion protein containing only the SH2 domains of Syp bound the Tyr(P) form of IRS1. Unlike the receptors for epidermal and platelet-derived growth factors, which in their activated state bind to the SH2 domains of Syp and elicit phosphorylation of Syp on tyrosine in intact cells, the Tyr(P) form of the insulin receptor did not bind to the SH2 domains of Syp, and no phosphorylation of Syp on tyrosine was detected in insulin-treated 3T3-L1 adipocytes. In combination with other findings these results indicate that IRS1 functions as a docking protein for SH2 domain-containing proteins participating in signaling from the insulin receptor.
胰岛素受体底物1（IRS1）是一种在酪氨酸位点被激活的胰岛素受体快速磷酸化的蛋白质。Syp是最近发现的一种广泛表达的磷酸酪氨酸（Tyr(P)）磷酸酶，它含有两个Src同源结构域2（SH2）。我们发现，用胰岛素处理3T3-L1脂肪细胞会导致IRS1和Syp之间形成复合物。通过免疫印迹和Tyr(P)磷酸酶活性检测发现，在胰岛素处理的细胞提取物中，而非基础细胞提取物中，IRS1的免疫吸附物中能检测到Syp。Syp与IRS1的结合显然发生在Syp的SH2结构域和IRS1的含Tyr(P)序列之间，因为仅包含Syp的SH2结构域的融合蛋白能结合Tyr(P)形式的IRS1。与表皮生长因子受体和血小板衍生生长因子受体不同，后者在激活状态下能结合Syp的SH2结构域并在完整细胞中引发Syp酪氨酸磷酸化，胰岛素受体的Tyr(P)形式不与Syp的SH2结构域结合，并且在胰岛素处理的3T3-L1脂肪细胞中未检测到Syp酪氨酸磷酸化。结合其他研究结果，这些结果表明IRS1作为一种对接蛋白，参与含SH2结构域的蛋白质介导的胰岛素受体信号转导。
