Karlsson T, Welsh M
Department of Medical Cell Biology, Uppsala University, Sweden.
Exp Cell Res. 1997 Mar 15;231(2):269-75. doi: 10.1006/excr.1996.3471.
In the present study we have investigated a possible role for the proline-rich SH2 domain protein Shb as a regulator of expression or activity of certain SH3 domain proteins and MAP kinase. The expression of the Shb binding proteins Eps8, Src, and p85 PI3-kinase, PI3-kinase activity, and MAP kinase activation were assessed in wild-type NIH3T3 cells and in NIH3T3 cells overexpressing the Shb cDNA. In addition, the expression of the SH3 domain STAT1 proteins was assessed in wild-type and Shb overexpressing cells. The Eps8 protein content and Eps8 mRNA steady-state levels were downregulated, whereas the protein contents of Src and p85 PI3-kinase were unaffected by Shb overexpression. There was, however, an increased basal PI3-kinase activity in Shb transfected cells after a 3-h serum starvation. Increased steady-state levels of STAT1 mRNA were accompanied by an increased STAT1 protein content in Shb overexpressing cells. Shb overexpression was not associated with an altered activation of p44 or p42 MAP kinases in response to PDGF stimulation. The data presented in this study suggest novel functions for the adaptor protein Shb regulating the expression of certain signal-transducing SH3 domain proteins and modulating PI3-kinase activity.
在本研究中，我们研究了富含脯氨酸的SH2结构域蛋白Shb作为某些SH3结构域蛋白和丝裂原活化蛋白激酶（MAP激酶）表达或活性调节因子的潜在作用。在野生型NIH3T3细胞和过表达Shb cDNA的NIH3T3细胞中，评估了Shb结合蛋白Eps8、Src和p85磷脂酰肌醇-3激酶（PI3-激酶）的表达、PI3-激酶活性以及MAP激酶激活情况。此外，还在野生型细胞和过表达Shb的细胞中评估了SH3结构域信号转导和转录激活因子1（STAT1）蛋白的表达。Eps8蛋白含量和Eps8 mRNA稳态水平下调，而Src和p85 PI3-激酶的蛋白含量不受Shb过表达的影响。然而，在3小时血清饥饿后，转染Shb的细胞中基础PI3-激酶活性增加。在过表达Shb的细胞中，STAT1 mRNA稳态水平升高伴随着STAT1蛋白含量增加。Shb过表达与血小板衍生生长因子（PDGF）刺激后p44或p42 MAP激酶的激活改变无关。本研究呈现的数据表明衔接蛋白Shb在调节某些信号转导SH3结构域蛋白的表达和调节PI3-激酶活性方面具有新功能。
