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细胞因子失调在人类疾病中的机制。该计划的总体目标是确定可能决定细胞因子特异性和冗余的信号分子和基因。在过去的资助期内，我们重点研究了白细胞介素(IL)-9介导的信号转导机制，IL -9是1988年由PI首次克隆的细胞因子。我们比较了IL-9介导的信号事件，IL-9是一种IL-2受体γ链（IL-2Rgamma）超家族细胞因子，与同一超家族中的其他细胞因子（如IL-4）。我们已经确定了几个信号分子，它们可能决定细胞因子的特异性（如STATs， irs, Tip60, 14-3-3）和冗余（如Cited2）的lL-2Rgamma超家族细胞因子。在下一个授权期内，我们希望进一步研究分子，根据过去授权期间发现的一些新发现，确定IL-4和IL-9之间的特异性。我们已经证明(1)在IL-9刺激下，Tip60 （tad相互作用蛋白，60 kDa）可以被Jak1和Jak3酪氨酸磷酸化，但不能被IL-4刺激；(2)Tip60以泛素化依赖的方式快速降解，并且Tip60的酪氨酸磷酸化是Tip60蛋白稳定所必需的；(3)Tip60与内源性Stat3复合物，并调节IL-9诱导的Stat3核易位。(4) Tip60作为STAT3的共同抑制因子，通过募集去乙酰化酶HDAC7来调节基因表达；(5)STAT3在IL-9刺激后乙酰化，这种乙酰化可以被Tip60 HAT-突变体消除；(6)Nmi和importin-alpha7是新发现的Tip60相互作用蛋白，这两个蛋白被证明参与ifn - γ信号传导和IL-2。基于我们和其他人的新发现，我们假设(1)Tip60/ il - 9rα相互作用和STAT3乙酰化对STAT3介导的功能很重要；(2)对Tip60相互作用蛋白如Nmi和importin-alpha7的表征可能揭示核转运和STATs激活/失活的新机制。为了验证这些假设，我们将(1)通过分析STAT3乙酰化对核易位、dna结合、转录激活和STAT3介导的生物学功能的影响，研究Tip60/IL-9Ralpha相互作用和STAT3乙酰化的机制和生物学意义；（II）通过分析Nmi和importin-alpha7对核易位、dna结合、转录激活和STAT3介导的生物学功能的影响，研究Tip60及其相互作用蛋白在STAT激活中的作用。STAT3/Tip60介导的转录激活和生物学功能。该提案结合了当前几个重要的研究领域，包括细胞因子特异性/冗余，核输入/输出，蛋白质磷酸化/泛素化/乙酰化/去乙酰化，转录激活/抑制和细胞因子介导的细胞功能。预计这项研究的完成将进一步加深我们对细胞因子信号转导的控制机制的理解，这可能会导致癌症和白血病/淋巴瘤的新治疗方式。

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.