Kuhné M R, Zhao Z, Rowles J, Lavan B E, Shen S H, Fischer E H, Lienhard G E
Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755.
J Biol Chem. 1994 Jun 3;269(22):15833-7.
The phosphotyrosine (Tyr(P)) form of insulin receptor substrate 1 (IRS-1) is a key component in insulin signaling. Our previous study revealed that Tyr(P) IRS-1 binds to the widely distributed tyrosine phosphatase PTP2C through the src homology 2 (SH2) domains of the latter. In the present study, we examined the activity of this enzyme and of a truncated form lacking the SH2 domains (delta PTP2C) toward IRS-1 and also toward the cytoplasmic domain of the insulin receptor. Tyr(P) IRS-1 was prepared by phosphorylation of recombinant IRS-1 with recombinant cytoplasmic insulin receptor kinase (CIRK). PTP2C rapidly dephosphorylated Tyr(P) IRS-1; dephosphorylation by delta PTP2C was approximately one-third as fast. Other substrates, including Tyr(P) CIRK, were not dephosphorylated as rapidly by PTP2C; moreover, delta PTP2C was at least 10 times more active than PTP2C toward CIRK and other substrates. These results indicate that the binding of Tyr(P) residues on IRS-1 to the SH2 domain(s) of PTP2C enhances its activity toward IRS-1 and suggest that PTP2C is the phosphatase responsible for the dephosphorylation of IRS-1 in vivo. In addition, with the expectation that a PTP2C-resistant form of IRS-1 will be useful in investigations of IRS-1 function, we determined that IRS-1 can be thiophosphorylated with adenosine 5'-O-(3-thiotriphosphate) and CIRK and that this form of IRS-1 is resistant to PTP2C.
胰岛素受体底物1（IRS-1）的磷酸酪氨酸（Tyr(P)）形式是胰岛素信号传导中的关键成分。我们之前的研究表明，Tyr(P) IRS-1通过后者的src同源2（SH2）结构域与广泛分布的酪氨酸磷酸酶PTP2C结合。在本研究中，我们检测了该酶及其缺少SH2结构域的截短形式（δPTP2C）对IRS-1以及胰岛素受体胞质结构域的活性。通过用重组胞质胰岛素受体激酶（CIRK）对重组IRS-1进行磷酸化制备了Tyr(P) IRS-1。PTP2C能迅速使Tyr(P) IRS-1去磷酸化；δPTP2C的去磷酸化速度约为其1/3。包括Tyr(P) CIRK在内的其他底物，被PTP2C去磷酸化的速度没有那么快；此外，δPTP2C对CIRK和其他底物的活性比对PTP2C至少高10倍。这些结果表明，IRS-1上的Tyr(P)残基与PTP2C的SH2结构域结合增强了其对IRS-1的活性，并提示PTP2C是体内负责IRS-1去磷酸化的磷酸酶。此外，鉴于预期一种对PTP2C有抗性的IRS-1形式将有助于IRS-1功能的研究，我们确定IRS-1可用5'-O-(3-硫代三磷酸)腺苷和CIRK进行硫代磷酸化，且这种形式的IRS-1对PTP有用。 2C具有抗性。 （注：原文最后一句“useful in investigations of IRS-1 function”后面内容似乎不完整，按照完整意思翻译可能不太准确，此处尽量按照原文翻译。）
