IL-2 Receptors--Molecular Regulation of Receptor Express

人类白细胞介素-2受体和相关的细胞因子/细胞因子受体系统正在研究中，以了解正常和肿瘤细胞中T细胞免疫应答的关键组成部分。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。gc是IL-4、IL-7、IL-9、IL-15和IL-21的受体也使用的共享链，并且是在XSCID中突变的蛋白质。该小组主要关注IL-2诱导的信号类型，特别是STAT蛋白（信号转导和转录激活因子）的激活，以及它们调节IL-2 Ra基因和其他IL-2诱导基因的机制。在随附的年度报告中，总结了我们已经报道了大量受gc依赖性细胞因子调控的基因的特征。其中许多似乎依赖于两个密切相关的Stat 5蛋白，表示Stat 5a和Stat 5 b，我们以前已经证明，这两种蛋白质通过结合两个广泛分离的IL-2反应元件来严格控制IL-2受体α链基因调控。通过DNA芯片和SAGE方法，对IL-2调控的基因进行了更详细的研究。除了发现大量新基因外，还发现并报道了一些基因以“簇”的形式出现。关于IL-2 Ra基因调控本身，该小组在鉴定IL-2 Ra基因中的TGF β反应元件方面取得了进展，现在已经对其进行了表征和报道。 Stat 5a和Stat 5 b是两种密切相关的蛋白质，具有>90%的氨基酸同一性，由IL-2激活。编码Stat 5a和Stat 5 b的基因是相邻的，并且基因以头对头的方向定位。一个重要的问题是，这些密切相关的蛋白质在它们的作用中是否是多余的或独特的。为了试图澄清这个问题，产生Stat 5a和Stat 5 b转基因小鼠以重建敲除小鼠。此外，正在研究这些基因调控的相似性与差异性。Stat 5a和Stat 5 b转基因小鼠的表型显著。我们的研究表明，这些蛋白质在调节CD 8 + T细胞稳态中起着重要作用，并报道了这些发现。此外，随着小鼠年龄的增长，它们发展为胸腺淋巴母细胞淋巴瘤，即使它们没有表现出组成性激活的Jak-STAT通路。以前，我们和其他人证明，组成性激活的Jak-STAT通路与某些恶性肿瘤的发展相关，可能是因果关系。 在相关的报告中，值得注意的是，我们以前证明了IL-7受体α链的表达受到IL-2的有效负调控。虽然有一些关于B细胞中IL-7受体调节基础的信息，但在T细胞中基本上一无所知。在B细胞中，Ets家族转录因子PU. 1对于基因的控制至关重要。我们定义并报道了该基因的转录起始位点，并发现在B细胞中结合PU. 1的相同Ets结合位点对于T细胞中IL-7 Ra的表达也是必需的，但在T细胞中，关键因素是GA结合蛋白（GABP）。我们通过基因捕获方法产生了GABPalpha水平降低的小鼠。GABPa表达减少的胚胎表现出胸腺细胞数量明显减少，这些细胞上的IL-7 Ra减少。相反，胎肝B细胞具有正常水平的IL-7 R表达。这些数据表明，不同淋巴谱系中IL-7 Ra的差异调节至少部分通过将因子差异募集至相同GGAA基序来实现。后一项调查结果都是去年报告的。 最后，与IL-21的研究相关，该小组在表征IL-21基因调控基础方面取得了重大进展，并报告了这些发现。此外，关于T细胞受体介导的IL-21受体表达的增加已经了解了很多。 这些发现增强了我们对调控免疫反应的基因表达控制机制的理解，在未来具有潜在的治疗意义。

The human interleukin-2 receptor and related cytokine/cytokine receptor systems are 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. gc is a shared chain also used by the receptors for IL-4, IL-7, IL-9, IL-15, and IL-21, and is the protein that is mutated in XSCID. The group has focused primarily on the types of signals induced by IL-2, particularly the activation of STAT proteins (signal transducers and activators of transcription), and the mechanism by which they regulate the IL-2Ra gene and other IL-2 induced genes. In the accompanying annual report, it is summarized that we have reported the characterization of a large number of genes that are regulated by gc dependent cytokines. Many of these appear to be dependent on two closely-related Stat5 proteins, denoted Stat5a and Stat5b, and we have previously demonstrated that these two proteins critically control IL-2 receptor alpha chain gene regulation by binding to two widely separated IL-2 response elements. The genes regulated by IL-2 were studied in greater detail, both by DNA array and SAGE methodology. In addition to identifying a large number of new genes, it was discovered and reported that some of the genes occur in "clusters". Regarding IL-2Ra gene regulation itself, the group made progress in the identification of a TGFbeta response element in the IL-2Ra gene, which now has been characterized and reported. Stat5a and Stat5b are two closely related proteins with >90% amino acid identity that are activated by IL-2. The genes encoding Stat5a and Stat5b are adjacent and the genes are located in a head-to-head orientation. An important issue is whether these closely related proteins are redundant or distinctive in their actions. To attempt to clarify this issue, Stat5a and Stat5b transgenic mice were generated to reconstitute the knockout mice. In addition, aspects of similarities vs. differences in regulation of these genes are being studied. The phenotype of Stat5a and Stat5b transgenic mice was striking. Our studies revealed that these proteins play a major role in the regulation of CD8+ T cell homeostasis and these findings were reported. Moreover, as the mice aged, they developed thymic lymphoblastic lymphoma, even though they did not exhibit a constitutively activated Jak-STAT pathway. Previously, we and others demonstrated that a constitutively activated Jak-STAT pathway correlates with and perhaps is causal in the development of certain malignancies. In the associated report, it is noted that we previously demonstrated that IL-7 receptor alpha chain expression is potently negatively regulated by IL-2. Although there is some information regarding the basis for regulation of the IL-7 receptor in B cells, essentially nothing was known in T cells. In B cells, an Ets family transcription factor, PU.1, is critical for control of the gene. We defined and reported the transcription initiation site for the gene, and discovered that the same Ets binding site that binds PU.1 in B cells is also essential for IL-7Ra expression in T cells, but that in T cells, the critical factor is GA binding protein (GABP). We generated mice with diminished levels of GABPalpha by a gene-trap methodology. Embryos with diminished expression of GABPalpha exhibited marked diminished numbers of thymocytes and diminished IL-7Ra on those cells. In contrast fetal liver B cells had normal levels of IL-7R expression. These data indicate that differential regulation of IL-7Ra in distinct lymphoid lineages is achieved at least in part by differential recruitment of factors to the same GGAA motif. These latter findings were all reported in the past year. Finally, related to its study of IL-21, the group made major progress in characterizing the basis for regulation of the IL-21 gene and these findings were reported. Moreover, much has been learned about T-cell receptor mediated increases in the expression of the receptor for IL-21. These findings enhance our understanding of mechanisms controlling expression of genes that regulate the immune response, with potential therapeutic implications in the future.