Targeting RIP1-mediated pathways for immune homeostasis and tolerance

 描述（由申请人提供）：本项目的重点是研究RIPK1（RIP或RIP1），这是我们和其他人最近的研究中发现的一种新的自身免疫性疾病参与者。我们假设RIP1可能是一种介质，在各种自身免疫性疾病，通过激活促生存/增殖信号。因此，以RIP1为目标可以 作为一种有效的治疗方法Fas（Apo-1或CD95）基因突变可导致具有狼疮某些特征的自身免疫淋巴增生（lpr）综合征（ALPS）。RIP1最初被鉴定为一种潜在的Fas相互作用蛋白。随后的研究表明，RIP1也是肿瘤坏死因子受体1（TNFR1）信号复合物的一个组成部分。结果，Fas-/-TNFR1-/-双突变小鼠发展加速的lpr疾病。然而，由于RIP1缺陷小鼠的围产期致死性，RIP1的生理功能知之甚少。使用一种新的条件突变动物模型，我们的初步数据表明，RIP1在T细胞中起着关键作用。在我们以前的研究中，RIP1缺陷能够挽救缺乏FADD的小鼠的胚胎致死率，FADD是Fas或TNFR 1通过招募和激活启动子caspase 8诱导的细胞凋亡的介体。这一发现标志着我们对程序性细胞死亡（PCD）理解的转折点，揭示了RIP1在体内介导的强有力的坏死性凋亡（程序性坏死）途径。然而，目前还不清楚为什么RIP1-/-小鼠和RIP1-/-FADD-/-双突变小鼠显示围产期致死性。与此相反， 在缺乏FADD和RIP3的动物中，胚胎和出生后发育是正常的。后者是RIP1的同源物，并且专门发出坏死性凋亡的信号。因此，FADD的缺乏会导致坏死，这取决于RIP1和/或RIP3。由此产生的RIP1-/-FADD-/-双突变小鼠发生ALPS/lpr，其比Fas突变小鼠中的更严重。在这里，我们假设靶向RIP1将促进细胞死亡，并作为治疗lpr-自身免疫性疾病的策略。然而，RIP1在免疫系统中的这种新功能的调节机制还不清楚。因此，我们建议：1）测试RIP1功能的遗传和药理学消除对抑制lpr-自身免疫性疾病的作用; 2）阐明由RIP1介导的原代淋巴细胞中的促存活途径; 3）通过体内功能互补研究鉴定RIP1蛋白中的结构/功能结构域/基序，以促进药物设计。这些特定目标的成功完成将为RIP1调节机制提供新的见解，并导致淋巴组织增生性，自身免疫性和相关疾病的治疗方法的更好设计。

 DESCRIPTION (provided by applicant): The focus of this project is to investigate RIPK1 (RIP or RIP1), a novel player in autoimmune diseases, as revealed in recent studies by us and others. We hypothesize that RIP1 could be a mediator in a variety of autoimmune conditions through activation of a pro-survival/proliferation signaling. Therefore, targeting RIP1 could serve as an effective therapeutic approach. Gene mutations in Fas (Apo-1 or CD95) could lead to an autoimmune-lymphoproliferative (lpr) syndrome (ALPS) with certain characteristics of lupus. RIP1 was originally identified as a potential Fas-interacting protein. Subsequent studies indicate that RIP1 is also a component of the signaling complex of tumor necrosis factor receptor 1 (TNFR1). As a result, Fas-/-TNFR1-/- double mutant mice develop accelerated lpr diseases. However, the physiological function of RIP1 is poorly understood due to perinatal lethality in RIP1-deficient mice. Using a novel conditional mutant animal model, our preliminary data indicates that RIP1 plays a critical role in T cells. In our previous study, RIP1 deficiency was able to rescue embryonic lethality in mice lacking FADD, a mediator of apoptosis induced by Fas or TNFR1 through recruiting and activating the initiator caspase 8. This discovery marks a turning point in our understanding of programmed cell death (PCD), by revealing a potent necroptosis (programmed necrosis) pathway mediated in vivo by RIP1. However, it remains unclear why RIP1-/- mice and RIP1-/- FADD-/- double mutant mice display perinatal lethality. In contrast, embryonic and postnatal development was normal in animals lacking both FADD and RIP3. The latter is a homologue of RIP1 and exclusively signals necroptosis. Therefore, absence of FADD unleashes necrosis, which is dependent on RIP1 and/or RIP3. The resulting RIP1-/-FADD-/- double mutant mice develop ALPS/lpr, which are more severe than that in Fas mutant mice. Here, we hypothesize that targeting RIP1 would promote cell death and serves as a strategy for treating lpr-autoimmune disease. However, the regulatory mechanism of this novel function of RIP1 in the immune system is not well understood. Therefore, we propose: 1) to test for the effect of genetic and pharmacological ablation of RIP1 function on suppressing lpr-autoimmune diseases; 2) to elucidate the pro-survival pathway(s) in primary lymphocytes that is mediated by RIP1; 3) to identify the structural/functional domain/motif in the RIP1 protein through in vivo functional complementation study, to facilitate drug design. Successful completion of these specific aims will provide new insights into the mechanisms regulated by RIP1 and lead to better design of therapies for lymphoproliferative, autoimmune and related diseases.