Jücker M, Feldman R A
Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore 21201, USA.
Curr Top Microbiol Immunol. 1996;211:67-75. doi: 10.1007/978-3-642-85232-9_7.
We have used a human GM-CSF-dependent hematopoietic cell line that responds to physiological concentrations of hGM-CSF to analyze a set of signaling events that occur in normal myelopoiesis and whose deregulation may lead to leukemogenesis. Stimulation of these cells with hGM-CSF induced the assembly of multimeric complexes that contained known and novel phosphotyrosyl proteins. One of the new proteins was a major phosphotyrosyl substrate of 76-85 kDa (p80) that was directly associated with the p85 subunit of phosphatidylinositol (PI) 3-kinase through the SH2 domains of p85. p80 also associated with the beta subunit of the activated hGM-CSF receptor, and assembly of this complex correlated with activation of PI 3-kinase. A second phosphotyrosyl protein we identified, p140, associated with the Shc and Grb2 adapter proteins by direct binding to a novel phosphotyrosine-interacting domain located at the N-terminus of Shc. and to the SH3 domains of Grb2, respectively. The Shc/p140/Grb2 complex was found to be constitutively activated in acute myeloid leukemia cells, indicating that activation of this pathway may be a necessary step in the development of some leukemias. The p80/p85/PI 3-kinase and the Shc/Grb2/p140 complexes were tightly associated with Src family kinases, which were prime candidates for phosphorylation of Shc, p80, p140 and other phosphotyrosyl substrates present in these complexes. Our studies suggest that p80 and p140 may link the hGM-CSF receptor to the PI 3-kinase and Shc/Grb2/ras signaling pathways, respectively, and that abnormal activation of hGM-CSF-dependent targets may play a role in leukemogenesis.
我们使用了一种依赖人GM-CSF的造血细胞系，该细胞系对生理浓度的hGM-CSF有反应，以分析一组在正常髓系造血中发生且失调可能导致白血病发生的信号事件。用hGM-CSF刺激这些细胞会诱导多聚体复合物的组装，这些复合物包含已知的和新的磷酸化酪氨酸蛋白。其中一种新蛋白是一种主要的76 - 85 kDa磷酸化酪氨酸底物（p80），它通过p85的SH2结构域与磷脂酰肌醇（PI）3激酶的p85亚基直接相关。p80还与活化的hGM-CSF受体的β亚基相关，并且这种复合物的组装与PI 3激酶的活化相关。我们鉴定的第二种磷酸化酪氨酸蛋白p140，分别通过直接结合位于Shc N端的一个新的磷酸酪氨酸相互作用结构域以及Grb2的SH3结构域，与Shc和Grb2衔接蛋白相关。发现Shc/p140/Grb2复合物在急性髓系白血病细胞中组成性活化，表明该信号通路的活化可能是某些白血病发生发展的必要步骤。p80/p85/PI 3激酶和Shc/Grb2/p140复合物与Src家族激酶紧密相关，Src家族激酶是这些复合物中Shc、p80、p140和其他磷酸化酪氨酸底物磷酸化的主要候选激酶。我们的研究表明，p80和p140可能分别将hGM-CSF受体与PI 3激酶和Shc/Grb2/ras信号通路相连，并且hGM-CSF依赖性靶点的异常活化可能在白血病发生中起作用。
