Swan K A, Alberola-Ila J, Gross J A, Appleby M W, Forbush K A, Thomas J F, Perlmutter R M
Howard Hughes Medical Institute, University of Washington School of Medicine, Seattle 98195.
EMBO J. 1995 Jan 16;14(2):276-85. doi: 10.1002/j.1460-2075.1995.tb07001.x.
Small molecular weight GTP binding proteins of the ras family have been implicated in signal transduction from the T cell antigen receptor (TCR). To test the importance of p21ras in the control of thymocyte development, we generated mice expressing a dominant-negative p21ras protein (H-rasN17) in T lineage cells under the control of the lck proximal promoter. Proliferation of thymocytes from lck-H-rasN17 mice in response to TCR stimulation was nearly completely blocked, confirming the importance of p21ras in mediating TCR-derived signals in mature CD4+8- or CD8+4- thymocytes. In contrast, some TCR-derived signals proceeded unimpaired in the CD4+8+ thymocytes of mice expressing dominant-negative p21ras. Analysis of thymocyte development in mice made doubly transgenic for the H-Y-specific TCR and lck-H-rasN17 demonstrated that antigen-specific negative selection occurs normally in the presence of p21H-rasN17. Superantigen-induced negative selection in vivo also proceeded unhindered in H-rasN17 thymocytes. In contrast, positive selection of thymocytes in the H-Y mice was severely compromised by the presence of p21H-rasN17. These observations demonstrate that positive and negative selection, two conceptually antithetical consequences of TCR stimulation, are biochemically distinguishable.
ras家族的小分子量GTP结合蛋白与T细胞抗原受体（TCR）的信号转导有关。为了测试p21ras在胸腺细胞发育控制中的重要性，我们构建了在lck近端启动子控制下在T谱系细胞中表达显性负性p21ras蛋白（H-rasN17）的小鼠。lck-H-rasN17小鼠胸腺细胞对TCR刺激的增殖几乎完全被阻断，这证实了p21ras在介导成熟CD4+8-或CD8+4-胸腺细胞中TCR衍生信号方面的重要性。相比之下，在表达显性负性p21ras的小鼠的CD4+8+胸腺细胞中，一些TCR衍生信号不受影响地进行。对H-Y特异性TCR和lck-H-rasN17双转基因小鼠的胸腺细胞发育分析表明，在存在p21H-rasN17的情况下，抗原特异性阴性选择正常发生。体内超抗原诱导的阴性选择在H-rasN17胸腺细胞中也不受阻碍地进行。相比之下，H-Y小鼠中胸腺细胞的阳性选择因p21H-rasN17的存在而严重受损。这些观察结果表明，阳性选择和阴性选择，这两个TCR刺激在概念上相反的结果，在生化上是可区分的。
