Zhao Q, Weiss A
Department of Medicine, University of California, San Francisco 94143-0724, USA.
Mol Cell Biol. 1996 Dec;16(12):6765-74. doi: 10.1128/MCB.16.12.6765.
The protein tyrosine kinase ZAP-70 plays an essential role in T-cell activation and development. After T-cell receptor stimulation, ZAP-70 is associated with the receptor and is phosphorylated on many tyrosine residues, including tyrosine 292 (Y-292), in the region between the C-terminal SH2 domain and the kinase domain (interdomain B). Here we show that a mutation of Y-292 (292F) or deletion of interdomain B enhanced the ability of ZAP-70 to reconstitute B-cell receptor stimulation-dependent NF-AT induction in a B-cell line deficient in Syk. In contrast, in a T-cell line, expression of 292F led to basal NF-AT induction independent of T-cell receptor stimulation. These results demonstrate that the role of Y-292 is to negatively regulate the function of ZAP-70 in lymphocytes. This appears to be a dominant function of interdomain B because deletion of most of interdomain B also resulted in a mutant of ZAP-70 with enhanced ability to reconstitute Syk-deficient DT-40 B cells. Since our biochemical studies did not reveal an effect of the 292F mutation on either the kinase activity of ZAP-70 or on the ability of ZAP-70 to bind to the receptor, we propose a model in which Y-292 interacts with an inhibitory protein to negatively regulate ZAP-70 function.
蛋白酪氨酸激酶ZAP-70在T细胞活化和发育过程中发挥着至关重要的作用。T细胞受体受到刺激后，ZAP-70与该受体结合，并在包括酪氨酸292（Y-292）在内的多个酪氨酸残基上发生磷酸化，这些酪氨酸残基位于C末端SH2结构域和激酶结构域之间的区域（结构域间B）。在此我们表明，Y-292的突变（292F）或结构域间B的缺失增强了ZAP-70在缺乏Syk的B细胞系中重建依赖B细胞受体刺激的NF-AT诱导的能力。相反，在T细胞系中，292F的表达导致了不依赖T细胞受体刺激的基础NF-AT诱导。这些结果表明，Y-292的作用是负向调节ZAP-70在淋巴细胞中的功能。这似乎是结构域间B的主要功能，因为结构域间B的大部分缺失也导致了ZAP-70的一个突变体，其重建Syk缺陷的DT-40 B细胞的能力增强。由于我们的生化研究未揭示292F突变对ZAP-70激酶活性或ZAP-70与受体结合能力的影响，我们提出了一个模型，其中Y-292与一种抑制性蛋白相互作用以负向调节ZAP-70的功能。
