全身性エリテマトーデス患者T細胞に発現されるTCRζ鎖の異常に関する研究

T细胞受体（TCR）刺激后最早的生化事件之一是细胞蛋白的酪氨酸磷酸化。对T细胞酪氨酸磷酸化的分析为研究T细胞功能缺陷提供了有力手段。为了探索SLE中观察到的T细胞功能障碍的分子和细胞机制，我们利用这些系统并检测了TCR/CD3和CD4刺激或不刺激SLE T细胞的酪氨酸磷酸化。当我们分析有或没有刺激的外周T细胞制备的总细胞裂解物的酪氨酸磷酸化时，在正常T细胞中总是检测到在18、56、70和100KD左右迁移的主要条带。相比之下，SLE T中pp18和pp100的酪氨酸磷酸化减少，而56KD波段的酪氨酸磷酸化正常至高水平。由于pp18似乎是TCR zeta链，因此从正常和SLE T细胞中免疫沉淀pp18，并检测其酪氨酸磷酸化和蛋白表达。TCR zeta链的酪氨酸磷酸化及其表达在60%以上的SLE患者中显著降低。在这些患者中，我们发现了一种没有外显子7或具有短外显子8的异常形式的zeta链，这可能是由选择性剪接产生的。在SLE T细胞中，随着zeta链表达的降低，适配蛋白和分子支架（如T细胞活化的连接物）在筏分数中不断被募集。这些结果可能解释了SLE T细胞的慢性激活状态，通过zeta链下调的无效负调控和随后缺乏蛋白酪氨酸磷酸酶（如SHP-2）。

One of the earliest biochemical events after T cell receptor (TCR) stimulation is the tyrosine phosphorylation of the cellular proteins. Analysis of the tyrosine phosphorylation in T cells have provided us powerful means to investigate the defects in T cell function. To explore the molecular and cellular mechanism of T cell dysfunction observed in SLE, we utilized these systems and examined tyrosine phosphorylation of SLE T cells with or without TCR/CD3 and CD4 stimulation.When we analyze the tyrosine phosphorylation of total cellular lysates prepared from peripheral T cells with or without stimulation, the major bands migrating around 18, 56, 70, and 100KD were always detected in normal T cells. In contrst, tyrosine phosphorylation was diminished in pp18 and pp100 in SLE T, whereas it was normal to high level in 56KD band.Since pp18 seemed to be TCR zeta chain, it was immunoprecipitated from normal and SLE T cells and examined for its tyrosine phosphorylation and protein expression. Tyrosine phosphorylation of the TCR zeta chain and its expression was significantly decreased in more than 60% of the SLE patients. Among those patients, we identified an aberrant form of zeta chain without exon7, or with short exon8, which are presumably generated from alternative splicing.Along with the decreased zeta chain expression in SLE T cells, adaptor proteins and molecular scafold such as linkers for activation of T cells are continuously recruited in the raft fraction. These results may account for the chronic activated status of SLE T cells, through ineffective negative regulation with downregulated zeta chain and subsequent lack of protein tyrosine phosphatase such as SHP-2.