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

描述(申请人提供)：结直肠癌是发达国家最致命的癌症之一，也是主要的死亡原因。不幸的是，对于许多患有慢性肠炎的人来说，结肠炎和结肠炎相关性癌症(CAC)的发病机制之间存在着强烈的联系。促炎症细胞因子肿瘤坏死因子-β及其下游的主要转录因子--核因子-βB是CAC的主要致病因子之一。因此，以核因子-β-B激活通路为靶点作为治疗或阻止CAC进展的一种手段，在研究人员中越来越受欢迎。最近，我们的实验室发现，具有生物活性的鞘氨醇-1-磷酸(S1P)及其产生的酶-鞘氨醇激酶1(SphK1)将持续的NF-β激活与慢性肠道炎症和CAC的发展联系在一起。S1P和SphK1长期以来一直与肿瘤坏死因子-β的作用有关。在典型的依赖于肿瘤坏死因子的细胞内信号级联反应中，一系列复杂的蛋白质相互作用和翻译后修饰调节信号的传播，最终导致基因转录。其中，受体相互作用蛋白-1、肿瘤坏死因子受体相关因子2(TRAF2)、细胞凋亡抑制因子1和2(cIAP1/2)起重要作用。然而，SphK1参与核因子-βB途径的分子机制尚不清楚。重要的是，SphK1和TRAF2在CAC患者的组织以及该疾病动物模型的结肠和肿瘤中都被证明是升高的。我的初步结果表明，SphK1、TRAF2和cIAP1/2之间的蛋白质-蛋白质相互作用对于它们的细胞稳定是重要的。因此，将在这一建议中检验的假设是，SphK1-TRAF2-cIAP1/2复合体通过直接的蛋白质-蛋白质相互作用调节每个蛋白质的稳定性、活性和功能，在核因子-βB的激活中发挥重要作用。我还认为，SphK1-TRAF2-cIAP1/2复合体的共同稳定有助于持续激活在结肠炎和CAC的慢性炎症中起重要作用的NF-β的前馈放大机制，并为结肠炎和CAC中SphK1和TRAF2的上调提供了解释。在第一个目的中，我将阐明SphK1-TRAF2-cIAP1/2共同稳定的分子机制，并检测它们对各自酶活性的共同调节作用。第二个目的是研究SphK1-TRAF2-cIAP1/2相互作用在调节核因子-β活化和相关生物反应中的作用。最后，第三个目的是研究SphK1和TRAF2的细胞自主功能以及它们在结肠炎和CAC小鼠模型中的相互作用。这一提议将为理解SphK1对慢性炎症和CAC的影响提供一个范式转换，历史上一直围绕S1P的形成及其对细胞增殖、抗凋亡和生存的多效性作用，并有望阐明SphK1在慢性炎症和CAC的病因学中的作用，并提供新的治疗策略来干扰这种致命疾病中核因子-βB途径的上调。

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.