Molecular Mechanisms Regulating Noncanonical NF-kB Signaling

描述(申请人提供)：核因子-B转录因子家族调节不同的生物过程，包括免疫反应、炎症、细胞生长和生存。核因子-B的激活涉及两条主要途径：规范途径和非规范途径。尽管对正则途径进行了广泛的研究，但对非正则途径仍知之甚少。由S等人率先开展的最新研究表明，非规范的NF-B途径的激活涉及抑制蛋白TRAF3的降解和NF-B诱导的激酶(NIK)的稳定。然而，这些信号事件是如何被负面控制的仍然是未知的。这一知识具有非常重要的意义，因为非规范的NF-B途径的非调控激活与严重的人类疾病有关，包括淋巴系统疾病和癌症。这一继续应用的总体目标是表征介导信号诱导的非规范核因子-βB信号负调控的分子机制。建议的研究是基于我们实验室高度创新的初步数据。特别是，我们已经确定了两个新的信号因子：去泛素酶OTUD7B和蛋白激酶TBK1，它们在非典范核因子-βB信号的负调控中起着关键作用。我们的数据表明，OTUD7B和TBK1可能在不同的信号步骤中发挥作用，以防止非规范的NF-βB的异常激活。使用新产生的OTUD7B基因敲除(KO)小鼠和TBK1条件性KO小鼠，我们获得的证据表明，OTUD7B和TBK1在调节抗体反应和维持肠道淋巴系统动态平衡方面发挥重要作用。肠道是一个动态的宿主-微生物区系相互作用的器官。我们的中心假设是OTUD7B和TBK1控制信号诱导的非规范核因子-βB激活的幅度，从而维持正常的免疫动态平衡和反应。为了解决这一假设并实现我们的总体目标，我们将(1)研究去泛素酶OTUD7B是如何控制信号诱导的TRAF3降解和非规范的NF-B激活的；(2)阐明TBK1调节NIK的命运和非规范的NF-B信号的幅度的机制；以及(3)表征OTUD7B和TBK1在体内调节非典型的NF-B信号和免疫功能的作用。S实验室率先开展的研究导致了非典范核因子-B途径的发现，并阐明了稳态非典范核因子-B调控的机制。我们相信，目前申请中提出的研究将再次导致该领域的重大进展，因为它们解决了目前未知的机制，即负向控制信号诱导的非典型核因子-B激活。除了概念上的创新，新产生的OTUD7B KO小鼠和TBK1条件性KO小鼠是研究非典范核因子-B信号的病理生理学的高度创新的模型。

DESCRIPTION (provided by applicant): The NF-¿B family of transcription factors regulates diverse biological processes, including immune response, inflammation, cell growth and survival. NF-¿B activation involves two major pathways: the canonical and noncanonical pathways. Despite the extensive studies of the canonical pathway, the noncanonical pathway is still poorly understood. Recent studies, pioneered by the PI¿s group, suggest that activation of the noncanonical NF-¿B pathway involves degradation of an inhibitory protein, TRAF3, and stabilization of the NF-¿B-inducing kinase (NIK). However, how these signaling events are negatively controlled is still unknown. This knowledge is highly significant, since deregulated activation of the noncanonical NF-¿B pathway is associated with severe human diseases, including lymphoid disorders and cancer. The overall objective of this continuation application is to characterize the molecular mechanisms mediating the negative regulation of signal-induced noncanonical NF-¿B signaling. The proposed studies are based on highly innovative preliminary data from our laboratory. In particular, we have identified two novel signaling factors the deubiquitinase Otud7b and the protein kinase TBK1, with pivotal roles in the negative regulation of noncanonical NF-¿B signaling. Our data suggest that Otud7b and TBK1 may act in different signaling steps to prevent aberrant activation of noncanonical NF-¿B. Using newly generated Otud7b knockout (KO) mice and TBK1 conditional KO mice, we have obtained evidence suggesting an important role for Otud7b and TBK1 in regulating antibody responses and maintaining lymphoid homeostasis in the intestine, an organ with dynamic host-microbiota interactions. Our central hypothesis is that Otud7b and TBK1 control the magnitude of signal-induced noncanonical NF-¿B activation and, thereby, maintain normal immune homeostasis and responses. To address this hypothesis and accomplish our overall objective, we will (1) examine how the deubiquitinase Otud7b controls signal-induced TRAF3 degradation and noncanonical NF-¿B activation; (2) elucidate the mechanism by which TBK1 regulates the fate of NIK and the magnitude of noncanonical NF-¿B signaling; and (3) characterize the in vivo role of Otud7b and TBK1 in regulating noncanonical NF-¿B signaling and immune functions. The PI¿s laboratory pioneered the studies that led to the discovery of the noncanonical NF-¿B pathway as well as to the elucidation of the mechanism underlying the steady-state noncanonical NF-¿B regulation. We believe that the studies proposed in the current application will once again lead to a major advancement of the field, since they address the currently unknown mechanism that negatively controls signal-induced noncanonical NF-¿B activation. In addition to the conceptual innovation, the newly generated Otud7b KO mice and TBK1 conditional KO mice serve as highly innovative models for studying the pathophysiology of noncanonical NF-¿B signaling.