Signaling of IL-2Rgamma Cytokines

描述（由申请人提供）：我的长期研究兴趣之一是了解细胞因子信号传导如何与生物功能相关的过程以及人类疾病中细胞因子失调的机制。该项目的总体目标是鉴定可能决定细胞因子特异性和冗余性的信号分子和基因。在过去的一段时间里，我们一直致力于研究白细胞介素（IL）-9介导的信号转导机制，IL-9是1988年PI首次克隆的细胞因子。我们比较了由IL-9（其是IL-2受体γ链（IL-2 R γ）超家族细胞因子）和同一超家族内的其它细胞因子（例如IL-4）介导的信号传导事件。我们已经鉴定了几种信号传导分子，其可以决定IL-2 R γ超家族细胞因子的细胞因子特异性（如STAT、IRS、Tip 60、14-3-3）和冗余性（如Cited 2）。在下一个授予期，我们希望进一步追求的分子，确定IL-4和IL-9之间的特异性基于几个新的发现发现在过去的授予期。我们已经证明：（1）Tip 60（Tat相互作用蛋白，60 kDa）在IL-9刺激后，而不是IL-4刺激后，可以被Jak 1和Jak 3酪氨酸磷酸化，（2）Tip 60以泛素化依赖的方式迅速降解，并且Tip 60的酪氨酸磷酸化是Tip 60蛋白稳定化所必需的，（3）Tip 60与内源性Stat 3复合，并调节由IL-9诱导的STAT 3的核转位，（4）Tip 60作为STAT 3的共阻遏物，通过募集脱乙酰酶HDAC 7来调节基因表达，（5）STAT 3在IL-9刺激后被乙酰化，并且乙酰化可以被Tip 60 HAT-突变体消除，以及（6）Nmi和输入蛋白-α 7，显示参与IFN-γ和IL-2信号传导的两种蛋白质是新鉴定的Tip 60相互作用蛋白质。基于我们和其他人的新发现，我们假设（1）Tip 60/IL-9 R α相互作用和STAT 3乙酰化对于STAT 3介导的功能是重要的，以及（2）Tip 60相互作用蛋白如Nmi和importin-alpha 7的表征可能揭示核转运和STAT激活/失活的新机制。为了验证这些假设，我们将（1）通过分析乙酰化STAT 3对核转位、DNA结合、转录激活和生物功能介导的STAT 3和（II）研究Tip 60及其相互作用蛋白在STAT激活通过分析Nmi和输入蛋白的影响，α 7对STAT 3/Tip 60介导的核转位、DNA结合、转录激活和生物学功能的影响。该建议结合了当前感兴趣的几个重要研究领域，包括细胞因子特异性/冗余，核输入/输出，蛋白磷酸化/泛素化/乙酰化/去乙酰化，转录激活/抑制和甘氨酸介导的细胞功能。预计该提案的完成将进一步加深我们对细胞因子信号转导控制机制的理解，这可能导致癌症和白血病/淋巴瘤治疗的新模式。

DESCRIPTION (provided by applicant): One of my long-term research interests has been to understand the process of how cytokine signaling correlates with biological functions and the mechanisms of cytokine dysregulation in human diseases. The overall goal of this program is to identify signaling molecules and genes that may determine cytokine specificity and redundancy. In the past granting period, we have focused on studying the signal transduction mechanisms mediated by interleukin (IL)-9, a cytokine first cloned by the PI in 1988. We have compared the signaling events mediated by IL-9, which is an IL-2 receptor gamma chain (IL-2Rgamma,) superfamily cytokine, and other cytokines (such as IL-4) within the same superfamily. We have identified several signaling molecules which may determine cytokine specificity (such as STATs, IRSs, Tip60, 14-3-3) and redundancy (such as Cited2) for lL-2Rgamma superfamily cytokines. In the next granting period, we would like to further pursue the molecules, which determine specificity between IL-4 and IL-9 based on several novel findings uncovered during the past granting period. We have shown that (1) Tip60 (Tat-interacting protein, 60 kDa) can be tyrosine phosphorylated by Jak1 and Jak3 following IL-9, but not IL-4, stimulation, (2) Tip60 is rapidly degraded in an ubiquitination-dependent manner, and tyrosine phosphorylation of Tip60 is required for the stabilization of the Tip60 protein, (3) Tip60 complexes with endogenous Stat3, and regulates nuclear translocation of STAT3 induced by IL-9, (4) Tip60 acts as a co-repressor for STAT3 to regulate gene expression by the recruitment of a deacetylase, HDAC7, (5) STAT3 is acetylated following IL-9 stimulation and the acetylation can be abrogated by Tip60 HAT- mutant and (6) Nmi and importin-alpha7, two proteins shown to be involved in the signaling of IFN-gamma, and IL-2, are newly identified Tip60 interacting proteins. Based on our novel findings and those of others, we hypothesize that (1) Tip60/IL-9Ralpha interaction and STAT3 acetylation are important for STAT3-mediated functions and (2) characterization of Tip60 interacting proteins such as Nmi and importin-alpha7 may uncover novel mechanisms of nuclear transport and activation/inactivation of STATs. To test these hypotheses, we will (1) Study the mechanism and biological significance of Tip60/IL-9Ralpha interaction and STAT3 acetylation by analyzing the effects of acetylated STAT3 on nuclear translocation, DNA-binding, transcriptional activation and biological functions mediated by STAT3 and (II) Study Tip60 and its interacting proteins in STAT activation by analyzing the effects of Nmi and importin-alpha7 on nuclear translocation, DNA-binding, transcription activation and biological functions mediated by STAT3/Tip60. This proposal combines several important research areas of current interests including cytokine specificity/redundancy, nuclear import/export, protein phosphorylation/ ubiquitination/ acetylation/ deacetylation, transcriptional activation/repression and cytokine-mediated cellular functions. It is anticipated the accomplishment of the proposal will further our understanding in the control mechanisms of cytokine signal transduction which may lead to new modalities of treatment for cancer and leukemia/lymphoma.