Paliogianni F, Boumpas D T
Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland 20892-1268, USA.
Transplantation. 1995 May 15;59(9):1333-9.
Glucocorticoids (GC) inhibit IL-2 gene transcription by interfering with the binding of the nuclear factor activator protein-1 on the IL-2 promoter. Calcineurin, a Ca2+/calmodulin-dependent protein phosphatase, is an essential component of the T cell antigen receptor signal transduction pathway leading to IL-2 gene transcription. Therefore, we have asked whether this phosphatase may also be regulated by GC. Jurkat T cells were cotransfected with plasmids containing the intact IL-2 promoter or its NF-AT and Oct-1 motifs, and a deletion mutant (delta CaM-AI) of calcineurin known to have Ca(2+)-independent constitutive phosphatase activity. Cotransfection of IL-2 promoter with delta CaM-AI allowed the activation of IL-2 promoter in the presence of phorbol ester alone. Under these conditions dexamethasone (Dex; 10(-6) M) inhibited IL-2 promoter activation by 50-60%. The inhibitory effect of Dex was specific, as demonstrated by experiments using an unrelated promoter (simian virus 40) and estradiol. Furthermore, it was completely reversed in the presence of excess amounts of the glucocorticoid antagonist RU 486, which suggests that it is mediated through the glucocorticoid receptor. Overexpression of calcineurin via delta CaM-AI in Jurkat cells decreased their apparent sensitivity to Dex (approximately 5-fold increase in IC50). Similar results were obtained with the NF-AT and Oct-1 constructs, which are also known to be activated by calcineurin. Thus, in addition to their known inhibitory effects on activator protein-1, GC also inhibit calcineurin-dependent pathways for T cell activation.
糖皮质激素（GC）通过干扰核因子激活蛋白-1与白细胞介素-2（IL-2）启动子的结合来抑制IL-2基因转录。钙调神经磷酸酶是一种Ca2+/钙调蛋白依赖性蛋白磷酸酶，是导致IL-2基因转录的T细胞抗原受体信号转导途径的重要组成部分。因此，我们研究了这种磷酸酶是否也受GC调节。将含有完整IL-2启动子或其核因子活化T细胞的胞浆因子（NF-AT）和八聚体转录因子-1（Oct-1）基序的质粒，与已知具有不依赖Ca(2+)的组成型磷酸酶活性的钙调神经磷酸酶缺失突变体（δCaM-AI）共转染到人 Jurkat T细胞中。IL-2启动子与δCaM-AI共转染可使仅在佛波酯存在时IL-2启动子激活。在这些条件下，地塞米松（Dex；10(-6) M）可抑制IL-2启动子激活50%-60%。使用无关启动子（猿猴病毒40）和雌二醇进行的实验表明，Dex的抑制作用具有特异性。此外，在存在过量糖皮质激素拮抗剂RU 486时，这种抑制作用完全逆转，这表明它是通过糖皮质激素受体介导的。通过δCaM-AI在Jurkat细胞中过表达钙调神经磷酸酶降低了它们对Dex的表观敏感性（半数抑制浓度（IC50）增加约5倍）。用NF-AT和Oct-1构建体也得到了类似结果，已知它们也可被钙调神经磷酸酶激活。因此，除了已知对激活蛋白-1的抑制作用外，GC还抑制T细胞激活的钙调神经磷酸酶依赖性途径。
