Molecular Mechanisms Regulating Noncanonical NF-kB Signaling

描述(申请人提供)：非规范的核因子-？B信号通路介导特定的核因子-？B成员p52和RelB的激活，调节重要的生物学功能，如破骨细胞生成、淋巴器官生成、淋巴细胞发育和激活，以及免疫耐受的产生。这一新的核因子-βB途径依赖于P52前体蛋白P100的处理。由于P100作为RelB的细胞质抑制物，P100的处理不仅产生P52，而且还导致活性P52/RelB核转录因子-？B复合体的核转位。在过去的几年里，我们已经取得了开创性的发现，证明P100的加工是通过其位点特异性的磷酸化受到严格调控的，这种磷酸化是由Nik和IKK1组成的新的激酶复合体组成的。我们的工作还揭示了人类T细胞白血病病毒(HTLV)转化的白血病T细胞中异常的P100处理。这一继续应用的总体目标是阐明调节正常和非规范的非典范核因子？B信号的分子机制。拟议的项目基于强大的初步数据和我们实验室发表的工作。特别是，我们最近的工作提出了一种新的NIK调节机制，似乎涉及到它与负调控因子TRAF3的动态相互作用，以及对其表达水平的调节。有趣的是，非规范的NF-B信号的诱导与TRAF3的降解有关，尽管这一中间信号步骤是如何调节的仍不清楚。我们的初步研究还揭示了新的非典范核因子-β信号调节因子的参与。此外，我们在了解白血病病毒HTLV对非典型核因子-βB的病理性激活方面取得了重大进展。基于这些发现，我们假设非规范的核因子-βB信号受负性和正性调节因子的严格控制，其调节的放松可能导致免疫紊乱和HTLV诱导的T细胞恶性肿瘤。我们将执行三个具体目标来检验我们的假设。(1)阐明调节NIK信号转导功能的生化机制。(2)表征非典型核因子-βB途径的中间信号步骤和分子组成。(3)探讨非典型性核因子-β途径在正常和病理性T细胞活化中的作用。与公共健康相关：核因子-？B转录因子家族调节不同的生物学过程，最显著的是免疫和炎症反应。本研究的重点是了解核因子-β活化的非典型(或非典型)信号通路。这一途径导致核因子？B亚群成员的激活，是特定适应性免疫功能所必需的，包括淋巴器官的形成、淋巴细胞的发育和激活。不受控制的非典型核因子？B信号与慢性炎症和自身免疫有关，而这一途径的缺陷会导致免疫缺陷。本申请中提出的研究涉及非规范的核因子-β信号的分子机制，并将对开发新的有效的免疫疗法具有重要意义。

DESCRIPTION (provided by applicant): The noncanonical NF-?B signaling pathway mediates activation of specific NF-?B members, p52 and RelB, which regulate important biological functions such as osteoclastogenesis, lymphoid organogenesis, lymphocyte development and activation, and generation of immunological tolerance. This novel NF-?B pathway relies on processing of the p52 precursor protein, p100. Since p100 functions as a cytoplasmic inhibitor of RelB, the p100 processing not only generates p52 but also causes nuclear translocation of active p52/RelB NF-?B complex. Over the past few years, we have made seminal pioneer findings demonstrating that the processing of p100 is tightly regulated through its site-specific phosphorylation by a novel kinase complex composed of NIK and IKK1. Our work also reveals the aberrant p100 processing in leukemia T cells transformed by the human T-cell leukemia virus (HTLV). The overall objective of this continuation application is to elucidate the molecular mechanisms mediating normal and deregulated noncanonical NF-?B signaling. The proposed project is based on strong preliminary data and published work from our laboratory. In particular, our recent work suggests a novel mechanism of NIK regulation, which appears to involve its dynamic interaction with a negative regulator, TRAF3, and modulation of its expression level. Intriguingly, induction of noncanonical NF-?B signaling is associated with TRAF3 degradation, although how this intermediate signaling step is regulated remains unclear. Our preliminary studies also reveal the involvement of novel regulators of noncanonical NF-?B signaling. Moreover, we have made significant progress towards understanding the pathological activation of noncanonical NF-?Bs by the leukemia virus HTLV. Based on these findings, we hypothesize that noncanonical NF-?B signaling is tightly controlled by negative and positive regulators, the deregulation of which may contribute to both immunological disorders and HTLV-induced T-cell malignancies. We will perform three specific aims to examine our hypotheses. (1) Elucidate the biochemical mechanisms that regulate the signaling function of NIK. (2) Characterize the intermediate signaling steps and molecular components of the noncanonical NF-?B pathway. (3) Investigate the role of noncanonical NF-?B pathway in normal and pathological T-cell activation. PUBLIC HEALTH RELEVANCE: The NF-?B family of transcription factors regulates diverse biological processes, most notably immune and inflammatory responses. The focus of this research project is to understand a noncanonical (or atypical) signaling pathway of NF-?B activation. This pathway leads to activation of a sub-group of NF-?B members and is required for specific adaptive immune functions, including lymphoid organ formation, lymphocyte development and activation. Uncontrolled noncanonical NF-?B signaling is linked to chronic inflammation and autoimmunity, whereas defect in this pathway causes immune deficiencies. The studies proposed in this application address the molecular mechanisms of noncanonical NF-?B signaling and will be important for the development of new and effective immune therapies.