类泛素化修饰Neddylation在疟原虫感染免疫中的作用及其机制

Malaria, an infectious disease caused by intracellular protozoan parasites of the genus Plasmodium, remains a devastating public health problem in the world. The pathology of malaria is caused by the asexual blood stage of the parasite’s life cycle, and the severity of the disease depends largely on the interplay between the infecting parasite and the immunological responses of the host. A better understanding of the regulatory mechanisms of immune responses against the blood-stage parasites will greatly facilitate the development of effective anti-malarial drugs and vaccines. Neddylation is a ubiquitylation-like pathway triggered by the conjugation of NEDD8 to specific targets and has emerged as a potential regulator of T cell function. However, its role in the protective immunity against blood-stage malaria is not clearly understood. In our previous study, we developed conditional knockout mice that lack UBA3, an essential subunit of the NEDD8 activating enzyme in T cells and investigated the correlation of neddylation with the immune responses to malarial parasite infection. We found this pathway plays an important role in regulating the proliferation and survival of CD4+ T cells as well as the development of effector Th1 cell subset. Furthermore, we demonstrated that the neddylation pathway is critical for the generation of parasite specific antibodies required for protection against Plasmodium yoelii 17XNL challenge. On the basis of these results, we prepare to explore the molecular mechanisms by which neddylation regulates CD4+ T-cell responses during the course of infection. More importantly, we will confirm the positive function of neddylation in the protection against blood-stage malaria by using NEDD8 conditional knockout mice. The study will add significantly to our understanding of the regulatory pathways in manipulating anti-malaria immunity and provide valuable information on the development of better control strategies for human malaria.

疟疾是由寄生于胞内的疟原虫引起的严重危害人类健康的传染病。加强对疟原虫感染后，特别是其致病阶段—红内期的宿主免疫应答及调控机制的理解，对于新型疫苗的研发和药物靶点的识别都具有重要意义。研究表明NEDD8介导的Neddylation修饰对T细胞功能具有潜在调控作用，但其在疟疾保护性免疫中的作用尚不明确。本项目前期我们利用T细胞中特异缺失NEDD8激活酶关键亚基—UBA3的小鼠模型开展了Neddylation与疟原虫感染免疫的相关性研究，结果提示Neddylation对疟原虫Py17XNL感染后CD4+ T细胞的增殖、分化和存活能力具有显著调控效应，且在感染中发挥了重要保护作用。在此基础上，我们将充分验证T细胞Neddylation修饰在疟原虫感染免疫中的作用并阐明介导其发挥免疫调控效应的信号途径和分子机制。本项目将拓展抗疟保护性免疫和调控途径的研究思路，为新型疟疾防治措施的开发提供有用信息。

疟疾是由寄生于胞内的疟原虫引起的严重危害人类健康的传染病。加强对疟原虫感染后，特别是其致病阶段—红内期的宿主免疫应答及调控机制的理解，对于新型疫苗的研发和药物靶点的识别都具有重要意义。研究表明小分子类泛素蛋白NEDD8介导的neddylation修饰对T细胞功能具有潜在调控作用，但其在疟疾保护性免疫中的作用尚不明确。本项目我们利用T细胞中特异缺失neddylation途径关键分子（如Uba3、NEDD8）的小鼠模型开展了其与疟原虫P.yoelii17XNL感染免疫的相关性研究，结果表明T细胞中neddylation途径的激活在感染进程中发挥了重要保护作用。其原因与该修饰途径对T细胞应答、特别是CD4+T细胞的活化、增殖、分化和存活的调控密切相关，进而影响了感染早期IFN-γ介导的炎症反应、感染后期生发中心的形成和疟原虫特异抗体的产生。在此基础上，我们阐明了neddylation对CD4+T细胞应答的调控与JNK通路活化水平的相关性，并且揭示了该修饰可通过促进Bcl-2分子表达抑制线粒体途径介导的CD4+T细胞凋亡。此外，我们还发现，Itch可作为重要的NEDD8底物在疟原虫感染中发挥作用，该修饰过程能够增强其作为泛素连接酶的活性，促进底物分子FoxO1的泛素化修饰和蛋白酶体途径降解，从而有效拮抗该分子在Tfh分化早期对关键转录因子Bcl-6表达的抑制作用，这是neddylation促进Tfh细胞分化和疟疾体液免疫应答建立的一个重要机制。本项目拓展了疟疾保护性免疫和调控途径的研究思路，可为新型防治措施的开发提供有用信息。同时，研究结论也将为机体抗其它病原体感染免疫的研究提供重要借鉴。