TIPE2诱导自噬的信号通路及其对巨噬细胞功能的调控

Autophagy is a critical process of maintaining cellular homeostasis, and plays a vital role in the innate immunity mediated by macrophages. Therefore, to explore the new molecules that regulate autophagy has important significance for clarifing the mechanism of autophagy in immune response. TIPE2 is a new negative immune regulator which suppresses immunocytes activation and the expression of inflammatory cytokines, and promotes cell death. However , the exact mechanism remains unknown. In preliminary experiment, we have found that TIPE2 promotes starvation-induced autophagy and blockage of autophagy reversed TIPE2-mediated cell death. Further study showes that TIPE2 suppresses the activity of Rac1, a member of the Rho family of GTPases, and autophagic regulator, mTOR. Blockage of Rac1 activity by inhibitor reduces TIPE2-mediated cell death. Therefore, in this study, based on our previous results, we will clerify whether TIPE2 promotes autophagy through targeting Rac1-mTOR axis and research the effect of TIPE2-mediated autophagy on macrophage autophagic cell death and cytokine production through using knockout or over expression system of genes, co-immunoprecipitation and confocal imaging et al. And investigate the role of TIPE2-mediated autophagy in inflammatory diseases by establishing the model of endotoxic shock in TIPE2-/- mice and blocking Rac1-mTOR pathways. This research not only has important theoretical significances for revealing the biological function and mechanism of TIPE2, but also will provide a new target for disease therapies.

自噬作为细胞自身稳定的重要方式，在巨噬细胞介导的固有免疫中发挥重要作用，发现调节自噬的新分子对阐明自噬在免疫应答中的作用有重要价值。TIPE2是新发现的免疫负调节分子，具有抑制免疫细胞活化、炎性细胞因子产生和促进细胞死亡的作用，但确切机制不清楚。我们前期研究发现TIPE2具有促进自噬的作用，阻断自噬可逆转TIPE2介导的细胞死亡；进一步发现TIPE2可抑制Rac1和自噬调节分子mTOR的活性。本课题拟在前期研究的基础上，采用基因敲除和过表达、免疫共沉淀和共聚焦显微成像等方法从TIPE2-Rac1-mTOR轴确定TIPE2促进自噬的信号通路、研究TIEP2介导自噬对巨噬细胞自噬性死亡和细胞因子分泌的调控并利用TIPE2基因敲除小鼠和内毒素休克等模型，通过阻断实验，研究TIPE2介导自噬在炎性疾病中的作用。该研究不仅对揭示TIPE2的功能和机制具有重要的理论价值，而且将为疾病的治疗提供新的靶点

Tipe2是肿瘤坏死因子-α介导的蛋白8样2 (TNFAIP8L2)，是先天免疫和适应性免疫的负性调节因子，在炎症稳态中发挥重要作用。已经证明，小鼠Tipe2直接结合并阻断Rac1 GTP酶活性，以确定先天免疫中吞噬和活性氧ROS爆发的强度。此外，Rac1被报道为哺乳动物雷帕霉素靶蛋白(rapamycin, mTOR)的关键激活因子，在营养刺激下通过与mTOR结合介导mTOR的充分活化。在这里，我们发现Tipe2可以通过竞争活性Rac1将溶酶体上的Rac1-mTORC1复合物分离，从而降低mTORC1的活性。相反，Tipe2的缺失或下调则会增强mTOR的激活。有趣的是，Tipe2不能通过谷氨酰胺和血清饥饿抑制mTOR活性来增加自噬流通畅。相反，在饥饿诱导的自噬中，它可能主要通过损伤自噬溶酶体再生(ALR)，来影响自噬的整个过程，而不是自噬起始。最后，我们证明Tipe2在自噬后期导致mTOR无法再活化，从而干扰自噬通量，导致细胞死亡。我们的研究揭示了Tipe2通过调控Rac1-mTORC1轴在自噬中的新作用，并支持其作为潜在治疗靶点。