血小板激活因子受体通过二聚化/多聚化调控下游信号通路的机制研究

G protein-coupled receptor (GPCR) are important drug targets and highly dynamic proteins that can adopt multiple ligand-induced conformations for their distinct signaling partners to deliver various cellular functions. Also some GPCR can assemble as dimers or higher-order oligomers, however the mechanism of downstream signaling modulation by dimerization/oligomerization is still not clear. Platelet-activating-factor receptor (PAFR) play an important role in many diseases. We choose platelet-activating-factor receptor (PAFR) as a prototype and find: PAFR could form dimer/oligomer and induce multiple downstram signaling. We first propose a hypothesis that PAFR could regulate signal transduction through dimerization/oligomerization. We intend to demonstrate the hypothesis from the following 3 aspects: (1) Detect the distribution of PAFR on cell membrane, and explore the interface of dimer/oligomer; (2) Elucidate the changes of different downstream signaling and internalization of PAFR after dimerization/oligomerization; (3) Screening of compounds that can affect the dimerization/oligomerization of PAFR, and detect their effects on different downstream signaling and internalization.This project will help to understand the mechanism of downstream signaling modulation by dimerization/oligomerization in PAFR, and provide a theoretical basis and a new idea for drug screening and development based on GPCR signal transduction.

G蛋白偶联受体（GPCR）是最重要的药物靶点,一些GPCR在被激动剂激活时,会引起多种下游信号通路；同时这些GPCR会发生二聚化/多聚化现象，但其通过二聚化/多聚化调控下游信号通路的机制不清。血小板激活因子受体（PAFR）在多种疾病发生中扮演着很重要的角色，申请者以PAFR为研究模型并发现：PAFR会发生二聚化/多聚化现象，并且可以激活多种信号通路。基于此,申请者推测PAFR可以通过二聚化/多聚化来调控下游不同的信号通路。本项目拟从以下三个方面进行论证：1）检测PAFR在细胞膜上的分布状态，并探究其二聚化/多聚化界面；2）检测PAFR发生二聚化/多聚化后，其下游不同信号通路的变化情况；3）筛选影响PAFR二聚化/多聚化的活性化合物，并检测其对下游不同信号通路的影响。本项目将有助于阐明PAFR通过二聚化/多聚化调控下游信号通路的机制，为基于GPCR靶点的药物研发提供理论依据和药物筛选新思路。

G蛋白偶联受体（GPCR）是最大的膜受体家族。大约三分之一的临床药物靶向该类受体。许多GPCR可以通过激活下游的G蛋白和阻遏蛋白（β-arrestin）来引起多种生理功能。不同的激动剂作用于同一个受体上时，引起的不同信号通路的激活被称为偏向性信号。但是GPCR怎么平衡多种细胞内信号通路的具体机制并不清楚。本研究中，我们发现血小板激活因子受体（PAFR）发生二聚化/多聚化后会引起不同的信号通路的激活：增强G蛋白信号通路，并降低β-arrestin的募集以及相关的受体内化。单分子成像结果显示PAFR在低表达量时即可以发生二聚化/多聚化。通过使用半胱氨酸交联策略，我们发现了两个对称的二聚化界面。相反，β-arrestin会阻碍受体发生二/多聚化。同时，我们发现了一个自然遗传突变体可以通过二聚化来引起偏向性信号的激活，暗示了该现象具有一定的生理学意义。该项目探究了GPCR和下游信号通路的关系，揭示了控制受体偏向性信号的新机制。

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