FAM134B介导内质网自噬对脓毒症时树突状细胞免疫功能影响及调控机制

FAM134B-mediated endoplasmic reticulum (ER)-phagy is one of the key mechanisms for maintaining functional homeostasis of ER, and critically involved in the pathogenesis and development of tumor and neurodegenerative disease, but the potential role and its regulatory mechanism on host immune system remains to be elucidated. The present project is aimed at exploring the effect of FAM134B-mediated ER-phagy on the immune function of dendritic cells, which might contribute to the development of sepsis-induced immune dysfunction. Firstly, it is scheduled to identify the activation of FAM134B-mediated ER-phagy in dendritic cells under sepsis exposure, and its relationship with immune dysfunction by combining in vivo and in vitro experiments. Secondly, the association between FAM134B-mediated ER-phagy and sepsis induced functional changes of dendritic cells will be clarified by using the septic models of both wild type mice and mice with FAM134B gene knockout. Thirdly, in order to explore the precise molecular mechanism for modulating ER-phagy, the possible role of ATF6 on the expression of FAM134B and activity of ER-phagy will be further investigated underlying the quality control of ER. Thus, the present study will be designed to understand the potential mechanism underlying sepsis-induced immune depression through deeply exploring the regulatory pathway of FAM134B-mediated ER-phagy on dendritic cells, and provide new therapeutic targets for modulating the host immune response in the setting of septic challenge.

FAM134B介导内质网自噬是维持内质网功能稳定的关键机制之一，参与肿瘤、神经退行性疾病的发生发展过程，而在免疫系统中的确切作用及调控机制尚不清楚。本项目旨在探讨FAM134B介导内质网自噬对树突状细胞(DC)免疫功能的影响及其在脓毒症免疫紊乱中的意义及作用。1.通过体内及体外实验明确脓毒症时FAM134B介导内质网自噬在DC中的活化规律，了解其与免疫功能紊乱的本质联系。2.采用野生型小鼠与FAM134B基因敲除小鼠脓毒症模型，澄清FAM134B介导内质网自噬在脓毒症时DC功能障碍中的作用。3.以内质网质量控制为切入点，深入探讨ATF6与FAM134B表达及内质网自噬活性的内在关系，揭示调控内质网自噬的信号转导途径。该研究从新的角度认识脓毒症免疫功能紊乱的发病过程，通过深刻了解FAM134B介导内质网自噬对DC免疫功能的影响及关键调控环节，将为脓毒症免疫调理提供新思路。

脓毒症是机体对感染的应答失控所致危及生命的器官功能障碍，被认为是重症监护病房患者最主要的死亡原因。树突状细胞（dendritic cell，DC）是体内功能最强大的抗原提呈细胞，能通过调节T细胞增殖及分化方向，进而影响免疫平衡状态。内质网自噬是内质网质量控制关键机制，能通过吞噬受损及肿胀内质网膜维持内质网结构及功能稳定，对细胞生存及功能发挥保护效应。本项目通过构建经典的盲肠结扎穿孔脓毒症动物模型观察发现，脓毒症早期内质网自噬关键受体FAM134B表达升高，内质网自噬活性增强，而脓毒症持续暴露下FAM134B表达及内质网自噬活性显著抑制。我们进一步比较野生型小鼠与FAM134B基因缺陷小鼠发现，与野生型小鼠比较，FAM134B基因缺陷小鼠DC功能活化明显抑制，表明FAM134B介导内质网自噬参与了DC成熟及活化过程，而其功能抑制可能是持续脓毒症暴露下DC应答紊乱的重要原因。基于内质网应激与内质网自噬在结构与功能上的密切互联，我们采用未折叠蛋白反应三条效应通路抑制剂发现，抑制ATF6活化能显著下调FAM134B表达及内质网自噬活化。我们进一步通过构建ATF6基因缺陷小鼠观察发现，与野生型小鼠比较，ATF6基因缺陷小鼠在脓毒症早期FAM134B表达及内质网自噬活化显著抑制，表明ATF6是启动内质网自噬的关键靶点。深入研究发现活化的ATF6能直接与FAM134B基因启动序列结合，促进FAM134B表达进而诱导内质网自噬活化。本项目充分阐明FAM134B介导内质网自噬在脓毒症状态下DC中的活化规律及其与DC功能活化的关系，证实脓毒症早期内质网应激反应激活，活化的ATF6能入核直接与FAM134B基因启动序列结合，促进FAM134B表达进而诱导内质网自噬活化，是启动内质网自噬的关键靶点。