IL2 RECEPTORS--MOLECULAR REGULATION

人类白细胞介素-2受体正在研究中，以了解正常和肿瘤细胞中T细胞免疫应答的关键成分。 T细胞活化后，IL-2和IL-2受体被诱导; T细胞免疫应答的幅度和持续时间由产生的IL-2的量、表达的受体水平和这些事件的时间过程控制。 存在IL-2受体的三条链，IL-2 Ra、IL-2 Rb和gc，其中IL-2 Ra和IL-2 Rb在转录水平上受到显著调节。 该小组主要关注IL-2诱导的信号类型，特别是STAT蛋白的激活，以及响应于有丝分裂原和IL-2调节IL-2 Ra基因表达的机制。 IL-2诱导的STAT蛋白（信号转导子和转录激活子）的研究取得了很大进展。IL-2可以激活新鲜人外周血淋巴细胞（PBL）中的Stat 5a和Stat 5 b（两种具有>90%氨基酸同一性的密切相关的蛋白质），并且另外激活用植物血凝素预激活的PBL中的Stat 3。 继续分析Stat 5a和Stat 5 b敲除小鼠。 以前，它表明，像Stat 5a敲除小鼠，Stat 5 b敲除小鼠也表现出自然杀伤细胞的增殖和细胞溶解活性的实质性缺陷。 在过去的一年中，已经证明Stat 5a和Stat 5 b都是抗原诱导的嗜酸性粒细胞和T细胞募集到组织中所必需的。与IL-2 Ra基因5'调节区中IL-2反应元件的存在一致，之前已表明，与Stat 5a敲除小鼠一样，Stat 5 b敲除小鼠在IL-2诱导的IL-2 Ra表达方面存在缺陷。 转基因方法被用于进一步研究Stat 5a和Stat 5 b的独特与重叠作用。 在合作研究中，该小组报告了HMG-I（Y）蛋白对IL-2受体α链启动子上定位的核小体赋予结构特异性的作用。 此外，IL-2 Ra基因中的另外的调节元件现在已经被表征。此外，据报道，从杆状病毒表达系统纯化的Stat 5a和Stat 5 b蛋白用于结合位点选择分析。 这揭示了Stat 5a和Stat 5 b二聚体都与类似的TTCN 3GAA基序结合，而Stat 5a四聚体表现出与比预期更大的位点库结合。 具体地，证明了除了典型的GAS基序之外，不同的“半GAS”基序或甚至更不相似的序列也对结合有重要贡献。更大的位点库也可能用作实现特定STAT蛋白与特定启动子结合的更大特异性的基础。 该实验室还致力于建立系统，以确定底物丝氨酸磷酸化在响应IL-2中的作用，并评估stat 5蛋白丝氨酸磷酸化的功能意义。总之，这些研究大大增强了我们对IL-2 R表达以及IL-2依赖性基因调控的基础的理解。

The human interleukin-2 receptor is being studied to understand critical components of the T cell immune response in normal and neoplastic cells. Following T-cell activation, IL-2 and IL-2 receptors are induced; the magnitude and duration of the T-cell immune response is controlled by the amount of IL-2 produced, the levels of receptors expressed, and the time course of these events. Three chains of the IL-2 receptor exist, IL-2Ra, IL-2Rb, and gc, with IL-2Ra and IL-2Rb being significantly regulated at the level of transcription. The group has focused primarily on the types of signals induced by IL-2, particularly the activation of STAT proteins, and the mechanism of regulating IL-2Ra gene expression in response to mitogen and IL-2. Considerable progress has been made in analyzing the STAT proteins (signal transducers and activators of transcription) induced by IL-2. IL-2 can activate both Stat5a and Stat5b (two closely related proteins with >90% amino acid identity) in fresh human peripheral blood lymphocytes (PBL) and additionally activates Stat3 in PBL preactivated with phytohemagglutinin. The analysis of Stat5a and Stat5b knockout mice was continued. Previously, it was shown that like Stat5a knockout mice, Stat5b knockout mice also exhibit a substantial defect in the proliferative and cytolytic activities of natural killer cells. In the past year, it was demonstrated that both Stat5a and Stat5b are required for antigen-induced eosinophil and T-cell recruitment into tissue. Consistent with the presence of an IL-2 response element in the 5' regulatory region of the IL-2Ra gene, it was previously shown that like Stat5a knockout mice, Stat5b knockout mice are defective in IL-2-induced IL-2Ra expression. Transgenic approaches are being used to further investigate distinctive vs. overlapping roles of Stat5a and Stat5b. In collaborative studies, the group reported the effect of HMG-I(Y) proteins on imparting architectural specificity to a positioned nucleosome on the IL-2 receptor alpha chain promoter. Moreover, an additional regulatory element in the IL-2Ra gene has now been characterized. Furthermore, it was reported that Stat5a and Stat5b proteins purified from a baculovirus expression system were used in a binding site-selection analysis. This has revealed that both Stat5a and Stat5b dimers bind to similar TTCN3GAA motifs, whereas Stat5a tetramers exhibit binding to a larger repertoire of sites than was expected. Specifically, it was demonstrated that in addition to canonical GAS motifs, divergent "half-GAS" motifs or even less similar sequences importantly contributed to binding. The larger repertoire of sites also likely serves as a basis for achieving greater specificity of binding of particular STAT proteins to particular promoters. The lab has also worked to set up systems to define the role of serine phosphorylation of substrates in response to IL-2, and to evaluate the functional significance of serine phosphorylation of stat5 proteins. Together, these studies substantially enhance our understanding of the basis for IL-2R expression as well as IL-2-dependent gene regulation.