Hashimoto K, Sohn S J, Levin S D, Tada T, Perlmutter R M, Nakayama T
Research Institute for Biological Sciences, Science University of Tokyo, Chiba, Japan.
J Exp Med. 1996 Sep 1;184(3):931-43. doi: 10.1084/jem.184.3.931.
The nonreceptor protein tyrosine kinase p56lck (Lck) serves as a fundamental regulator of thymocyte development by delivering signals from the pre-T cell receptor (pre-TCR) that permit subsequent maturation. However, considerable evidence supports the view that Lck also participates in signal transduction from the mature TCR. We have tested this conjecture by expressing a dominant-negative form of Lck under the control of a promoter element (the distal lck promoter) that directs high expression in CD4+CD8+ thymocytes, mature thymocytes, and peripheral T cells, thereby avoiding, complications that result from the well-documented ability of dominant-negative Lck to block very early events in thymocyte maturation. Here we report that expression of the catalytically inactive Lck protein at twice normal concentrations inhibits thymocyte positive selection by as much as 80%, while leaving other aspects of cell maturation intact. This effect was studied in more detail in mice simultaneously bearing the male-specific H-Y alpha/beta TCR transgene and ovalbumin-specific DO10 alpha/beta TCR transgene, where even equimolar expression of the dominant-negative Lck protein substantially vitiated the positive selection process. Although deletion of H-Y alpha/beta thymocytes proceeded normally in male mice despite the presence of catalytically inactive Lck, modest inhibition of superantigen-mediated deletion was in some cases observed. These data further implicate Lck in the propagation of all TCR-derived signals, and indicate that even very modest deficiencies in the representation of functional Lck molecules could in humans, profoundly alter the character of the peripheral TCR repertoire.
非受体蛋白酪氨酸激酶p56lck（Lck）通过传递来自前T细胞受体（pre-TCR）的信号来促进后续成熟，从而作为胸腺细胞发育的基本调节因子。然而，大量证据支持Lck也参与成熟TCR的信号转导这一观点。我们通过在启动子元件（远端lck启动子）控制下表达Lck的显性负性形式来验证这一推测，该启动子元件可在CD4 + CD8 +胸腺细胞、成熟胸腺细胞和外周T细胞中指导高表达，从而避免了显性负性Lck阻断胸腺细胞成熟早期事件的能力所导致的并发症。在此我们报告，催化失活的Lck蛋白以正常浓度的两倍表达时，可将胸腺细胞阳性选择抑制多达80%，而细胞成熟的其他方面保持完整。在同时携带雄性特异性H-Yα/β TCR转基因和卵清蛋白特异性DO10α/β TCR转基因的小鼠中对这一效应进行了更详细的研究，其中即使显性负性Lck蛋白等摩尔表达也会严重损害阳性选择过程。尽管存在催化失活的Lck，但雄性小鼠中H-Yα/β胸腺细胞的缺失仍正常进行，不过在某些情况下观察到超抗原介导的缺失受到适度抑制。这些数据进一步表明Lck参与所有TCR衍生信号的传递，并表明即使功能性Lck分子的表达存在非常轻微的缺陷，在人类中也可能深刻改变外周TCR库的特征。
