Gpr97在炎症应答中的作用及分子机制的研究

Tight regulation of NF-kB signaling is essential for innate and adaptive immune responses, yet the molecular mechanisms responsible for its negative regulation are not completely understood. Gpr97, an orphan adhesion GPCR, is highly expressed in immune cells. To explore the function of Gpr97 in immune system and the molecular mechanism involved, we generated a mouse model with global-targeted deletion of Gpr97. The phenotypic analyses have demonstrated an indispensable role of Gpr97 in maintaining B-lymphocyte population. By screening for the molecular events involved in the observed phenotypes, we found that lambda 5 expression is downregulated and its upstream inhibitor Aiolos is increased in the spleen of mutant mice, accompanied by significantly enhanced phosphorylation and nuclear translocation of cAMP response element-binding protein. Interestingly, increased constitutive NF-κB p50/p65 expression and activity were observed in the spleen of mutant mice, implicating a crucial role of Gpr97 in regulating NF-κB activity. In this project, we will make use of the Gpr97 knockout mouse model to characterize a role for Gpr97 in TLR-dependent or independent inflammatory responses. Furthermore, we attempt to identify the underlying mechanism(s) by which Gpr97 controls the inflammation. Results from these studies not only reveal more insights into the regulatory mechanism of innate immune system, but also provide useful target for manipulating amount responses against infections or inflammation-associated diseases, including cancer.

NF-κB信号通路的严密调控是固有免疫和适应性免疫应答所必需的，然而其负调控的分子机制尚不清楚。Gpr97是一个主要在免疫细胞表达的孤儿G蛋白偶联受体。课题组为研究该基因在免疫系统中的作用及其机制，建立了Gpr97基因剔除小鼠模型。表型分析表明Gpr97在B细胞发育过程中起到不可或缺的作用。此外相关分子机制研究显示，Gpr97缺失显著增加脾脏组织核提取物中的cAMP反应元件结合蛋白的磷酸化水平，且促进p50和p65蛋白的入核。这强烈提示该基因在NF-κB信号通路中的起到重要的调节作用。本项目将利用该基因剔除小鼠模型研究Gpr97在TLR依赖和非依赖的免疫反应中的作用，阐明Gpr97调控TLR信号通路和NF-κB的分子机制。这些研究结果能够帮助我们进一步了解Gpr97的生物学功能及其如何调控炎症反应的发生，而且在此基础之上有望为影响我国人民健康的感染性疾病的治疗提供理论基础和新的药物靶点。

多发性硬化症和其主要的动物模型-实验性自身免疫性脑脊髓炎(EAE)，是中枢神经系统的慢性炎症性疾病，该疾病的的特点是炎性脱髓鞘和神经变性， 抑制NF-κB信号转导通路可以减轻其发病症状。前期研究表明Gpr97可以调控NF-κB的活性。在本项目中，利用先前建立的Gpr97基因敲除小鼠模型，我们研究了Gpr97在小鼠中枢神经系统自身免疫性疾病中的作用。我们发现Gpr97基因缺失可以加重EAE的发病症状。与野生型同窝小鼠相比，Gpr97基因敲除小鼠的EAE临床评分更高，中枢神经系统中炎症细胞浸润和脱髓鞘现象更加严重， Th1和Th17细胞百分含量更高，炎症因子白介素-6、白介素-17、干扰素-γ和肿瘤坏死因子-α表达水平更高。体外细胞培养实验也证实了Gpr97可以调节促炎性细胞因子的产生。综上，我们的研究结果表明Gpr97对EAE疾病的发展至关重要，可能成为中枢神经系统自身免疫性疾病的新的治疗靶点。