SphK1-TRAF2-cIAP interactions in NF-kB activation, colitis and associated cancer

描述（由申请人提供）：结直肠癌是最致命的癌症之一，也是发达国家的主要死亡原因。不幸的是，对于许多慢性肠道炎症患者来说，结肠炎与结肠炎相关癌症（CAC）的发病机制之间存在密切联系。其中一个最好的特点CAC的贡献因素是促炎细胞因子TNF-β和其下游的主转录因子NF-？B。因此，针对NF-？B活化途径作为治疗或预防CAC进展的手段越来越受到研究人员的欢迎。最近，我们的实验室发现，生物活性鞘脂鞘氨醇-1-磷酸（S1 P）和酶，产生它，鞘氨醇激酶1（SphK 1），链接持久的NF-？B激活与慢性肠道炎症和CAC的发展。S1 P和SphK 1长期以来一直与TNF-α的作用有关。在典型的TNF依赖的细胞内信号级联导致NF-？B激活是一系列复杂的蛋白质相互作用和翻译后修饰，调节信号传播并最终导致基因转录。其中，受体相互作用激酶-1、TNF受体相关因子2（TRAF 2）和细胞凋亡抑制因子1和2（cIAP 1/2）发挥重要作用。然而，SphK 1参与NF-？B途径仍不清楚。重要的是，SphK 1和TRAF 2在CAC患者的组织以及该疾病动物模型的结肠和肿瘤中均显示升高。我的初步结果表明，SphK 1，TRAF 2和cIAP 1/2之间的蛋白质-蛋白质相互作用对它们的细胞稳定性很重要。因此，假设将在本提案中审查的是，SphK 1-TRAF 2-cIAP 1/2复合物在NF-？B通过直接的蛋白质-蛋白质相互作用激活，调节每种蛋白质的稳定性、活性和功能。我还建议，共同稳定的SphK 1-TRAF 2-cIAP 1/2复合物有助于前馈放大机制的持续激活NF-？B在结肠炎的慢性炎症和CAC的发展中起重要作用，并为结肠炎和CAC中SphK 1和TRAF 2的上调提供了解释。在第一个目标中，我将阐明SphK 1-TRAF 2-cIAP 1/2共稳定的分子机制，并检查对各自酶活性的共调节作用。第二个目的是研究SphK 1-TRAF 2-cIAP 1/2相互作用在NF-？B激活和相关的生物反应。最后，第三个目标是研究SphK 1和TRAF 2的细胞自主功能及其在结肠炎和CAC小鼠模型中的相互作用。这一建议将提供一个范式转变，了解SphK 1对慢性炎症和CAC的影响，这在历史上围绕着S1 P的形成及其对细胞增殖的多效性作用，保护细胞凋亡和生存，并希望澄清SphK 1在慢性炎症和CAC的病因学中的作用，并提供新的治疗策略，以干扰NF-？B途径在这种致命的疾病。

DESCRIPTION (provided by applicant): Colorectal cancer is one of the deadliest forms of cancer and a leading cause of death in developed countries. Unfortunately, for many with chronic bowel inflammation there is a strong link between colitis and the pathogenesis of colitis associated cancer (CAC). One of the best characterized CAC contributing factors is the pro-inflammatory cytokine TNF-¿ and its downstream master transcription factor NF-?B. Hence, targeting the NF-?B activation pathway as a means to treat or prevent CAC progression is gaining popularity among researchers. Recently, our laboratory discovered that the bioactive sphingolipid sphingosine-1-phosphate (S1P) and the enzyme that produces it, sphingosine kinase 1 (SphK1), link persistent NF-?B activation to chronic intestinal inflammation and development of CAC. S1P and SphK1 have long been implicated in the actions of TNF-¿. In the canonical TNF-dependent intracellular signaling cascade leading to NF-?B activation, a complex series of protein interactions and post-translational modifications modulate signal propagation and culminate in gene transcription. Among many others, the receptor interacting kinase-1, the TNF receptor associated factor 2 (TRAF2), and the cellular inhibitor of apoptosis 1 and 2 (cIAP1/2) play important roles. However, the molecular mechanism of the involvement of SphK1 in the NF-?B pathway has remained unclear. Importantly, both SphK1 and TRAF2 have been shown to be elevated in the tissues of patients with CAC and in the colons and tumors of animal models of the disease. My preliminary results suggest that protein-protein interactions between SphK1, TRAF2, and cIAP1/2 are important for their cellular stabilization. Hence, the hypothesis that will be examined in this proposal is that a SphK1-TRAF2-cIAP1/2 complex plays an important role in NF-?B activation by direct protein-protein interactions that regulate the stabiliy, activity and function of each protein. I also suggest that co-stabilization of the SphK1-TRAF2-cIAP1/2 complex contributes to the feed forward amplification mechanism for persistent activation of NF-?B important in chronic inflammation in colitis and development of CAC, and provides an explanation for the upregulation of SphK1 and TRAF2 in colitis and CAC. In the first aim I will elucidate the molecular mechanisms of SphK1-TRAF2-cIAP1/2 co-stabilization and examine co-regulatory effects on their respective enzymatic activities. The second aim will investigate the function of SphK1-TRAF2-cIAP1/2 interactions in the regulation of NF-?B activation and associated biological responses. Finally, the third aim examines the cell autonomous functions of SphK1 and TRAF2 and their interactions in murine models of colitis and CAC. This proposal will provide a paradigm shift in understanding the influence of SphK1 on chronic inflammation and CAC, which has historically revolved around formation of S1P and its pleiotropic effects on cellular proliferation, protection from apoptosis, and survival, and hopefully, clarify the role of SphK1 in the etiology of chronic inflammation and CAC and provide new therapeutic strategies to interfere with upregulation of the NF-?B pathway in this deadly disease.