The NF-kB Target, Gadd45Beta, in Lymphocytes and Liver

描述(申请人提供)：除了组织免疫和炎症反应外，核因子-kappaB还控制细胞存活。这种控制对于B淋巴细胞的生成、T细胞的动态平衡、肿瘤的发生以及对抗肿瘤因子α诱导的杀伤都是至关重要的。对于肿瘤坏死因子α，核因子-kappaB的抗凋亡活性涉及抑制JNK信号转导。使用无偏筛选，我们发现Gadd45beta/Myd118是这种抑制的关键中介，并发现其活性依赖于直接阻断JNK激酶MKK7/JNKK2。Gadd45beta是CD4+T细胞反应和保护肝脏免受外部挑战所必需的，这两个过程部分由JNK和NF-kappaB控制。然而，Gadd45β调节T淋巴细胞功能的机制(S)以及这种调节与体内获得性免疫的相关性尚不清楚。同样，Gadd45β在肝脏损伤反应中的确切作用仍有待确定。这项提案有三个具体目标，将同时解决这些问题。在目标1中，我们将通过体内方法，确定Gadd45β在T细胞稳态和获得性免疫反应中的生理功能及其对MAPK信号的调控。我们将从检测Gadd45beta-/-T细胞池在对抗原的生理反应过程中的扩张和收缩动力学开始。Gadd45beta的抗凋亡活性与外周T细胞缺失和记忆性T细胞发育的相关性将使用特征良好的模型来建立。在目标2中，我们将评估Gadd45β在生理性抗原启动期间体外控制T细胞功能的基础。利用这个系统，我们将建立Gadd45β消融对T细胞激活、增殖、TH1/TH2分化和AICD的精确影响。Gadd45beta对TCR诱导的MAPK通路的影响及其对T细胞功能的影响将被特别研究。在目标3中，我们将使用公认的肿瘤坏死因子α诱导、JNK介导的肝毒性模型，确定Gadd45β在肝脏损伤反应中作用的基础。特别是，我们将建立Gadd45β控制的JNK信号与肝脏中的NF-kappaB保护功能的相关性。肝细胞的功能也将在体外进行研究，在没有任何间质或组织影响的情况下。总之，这些研究可能为自身免疫、慢性炎症和癌症的机制提供重要的新见解，并可能为它们的治疗提供新的治疗工具。

DESCRIPTION (provided by applicant): In addition to marshalling immune and inflammatory responses, NF-kappaB controls cell survival. This control is crucial to B lymphopoiesis, T cell homeostasis, oncogenesis, and to antagonize TNFalpha-induced killing. With regard to TNFalpha the NF-kappaB anti-apoptotic activity involves the suppression of JNK signaling. Using an unbiased screen, we have identified Gadd45beta/Myd118 as a pivotal mediator of this suppression, and have found that its activity depends on direct blockade of the JNK kinase, MKK7/JNKK2. Gadd45beta is required for CD4+ T cell responses and hepato-protection from external challenge - two processes controlled in part by JNK and NF-kappaB. However, the mechanism(s) by which Gadd45beta regulates T lymphocyte function and the relevance of this regulation to adaptive immunity, in vivo, are not known. Likewise, the precise role of Gadd45beta in the liver response to injury remain to be determined. This proposal has three Specific Aims, which will address these issues concurrently. In Aim 1, by using an in vivo approach, we will determine the physiologic function of Gadd45beta, and its control of MAPK signaling, in T cell homeostasis and adaptive immune responses. We will begin by examining kinetics of expansion and contraction of the Gadd45beta-/- T cell pool during a physiologic response to antigen. The relevance of the Gadd45beta anti-apoptotic activity to peripheral T cell deletion and memory T cell development will be established using well-characterized models. In Aim 2, we will assess the basis for the Gadd45beta control of T cell function, during physiologic antigen-priming, ex vivo. Using this system, we will establish the precise effects of Gadd45beta ablation on T cell activation, proliferation, TH1/TH2 differentiation, and AICD. The impact of Gadd45beta on TCR-induced MAPK pathways and its consequences on T cell function will be specifically examined. In Aim 3, we will determine the bases for the role of Gadd45beta in the liver response to injury, using well-established models of TNFalpha-induced, JNK-mediated hepato-toxicity. In particular, we will establish the relevance of the Gadd45beta control of JNK signaling to the NF-kappaB protective function in the liver. Hepatocyte function will be also studied in vitro, in the absence of any stromal or organismal influences. Altogether, these studies may provide important new insights into mechanisms of autoimmunity, chronic inflammation, and cancer, and perhaps, new therapeutic tools for their treatments.