CCP2对3型固有淋巴样细胞发育分化的调控作用及分子机制研究

Study on mechanism of immune cell lineage commitment is a subject in the frontiers of medical field. Discovering the fate decision mechanisms of innate lymphoid cell development and differentiation will provide theoretical basis on regional immunology research and relative disease therapy. The development and differentiation of innate lymphoid cell is dependent on refined regulation of cytokines, signaling molecules and transcriptional factors. Glutamylation modification is involved in multiple life process. But the regulatory role of glutamylation in innate lymphoid cell development has not been reported yet. Our preliminary data show that CCP2 (Cytosolic carboxypeptidase 2) is highly expressed in common “helper-like” ILC lineage progenitors (CHILPs) and group 3 innate lymphoid cells (ILC3s). CCP2 deficiency results in increased ILC3 cells in small intestines of mice and upregulated IL22 production, which help the resistance to acute infection of C. rodentium. IL7Rα was identified as a substrate for CCP2. CCP2 intrinsically regulates glutamylation of IL7Rα and committed differentiation of precursor of innate lymphoid cell. This study is to further discuss the regulatory role of glutamylation for the development of ILC3, and to explore the molecular mechanism of glutamylation in promoting the development of ILC3 through IL7Rα and its downstream signaling.

免疫细胞谱系建立机制的研究是医学领域的前瞻课题，揭示固有淋巴样细胞发育分化的命运决定机制，将为区域免疫学研究和相关疾病的治疗提供理论依据。固有淋巴样细胞发育分化依赖细胞因子、信号分子和转录因子的精细调节。蛋白质的谷氨酸化修饰调控着多种生命活动，但对固有淋巴样细胞发育分化和谱系建立的调控作用尚未见报道。申请人的前期工作发现，胞内羧肽酶CCP2在固有淋巴样前体细胞（CHILP）和3型固有淋巴样细胞（ILC3）中高表达，CCP2基因敲除小鼠小肠ILC3比例明显升高，产生IL22量增加，使得小鼠可以有效抵抗柠檬酸杆菌感染。我们鉴定了IL7Rα为CCP2的底物，CCP2内源性的调控了IL7Rα的谷氨酸化修饰并调节了ILC前体细胞的定向分化。在此基础上，我们将深入探讨谷氨酸化修饰对ILC3细胞发育的调控作用，探明谷氨酸化修饰通过调控IL7Rα及下游信号促进ILC3发育的分子机制。

免疫细胞谱系建立机制的研究是医学领域的前瞻课题，揭示固有淋巴样细胞发育分化的命运决定机制，将为区域免疫学研究和相关疾病的治疗提供理论依据。固有淋巴样细胞的发育分化受到细胞因子、信号分子和转录因子等精细调控。ILC3类细胞表达RORγt和IL-22，包括NKp46+, NKp46- 及 CCR6+ LTi细胞等亚群，对机体抵抗肠道菌感染是必须的。蛋白质的谷氨酸化修饰调控着多种生命活动。我们的工作发现，胞内羧肽酶CCP2在固有淋巴样前体细胞（CHILP）和3型固有淋巴样细胞（ILC3）中高表达，CCP2基因敲除小鼠小肠ILC3比例明显升高，产生IL22量增加，使得小鼠可以有效抵抗柠檬酸杆菌感染。我们鉴定了IL7Rα为CCP2的底物。谷氨酸化酶TTLL4和TTLL13酶在αLPs 及CHILPs前体细胞高表达。TTLL4和TTLL13的缺失导致小鼠ILC3数量显著减少。TTLL4和TTLL13酶催化IL-7Rα的谷氨酸化，而CCP2催化谷氨酸化修饰侧链的切除。CCP2缺失导致IL-7Rα高度谷氨酸化，驱动STAT5激活和RORγt的表达，促进CHILPs到ILC3的分化过程，从而ILC3数量增加。TTLL4和TTLL13缺失则导致相反的表型。故此我们证明了IL7Rα的谷氨酸化修饰对ILC3细胞的分化是必须的。

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