应激影响猪GPR120受体功能及其內吞机制研究

G蛋白偶联受体（G protein-coupled receptor，GPR）120是一种长链脂肪酸受体，其参与调节机体糖脂代谢，介导炎症反应，近年来受人关注。但是GPR120的功能在猪上研究很少。前期实验中我们发现应激后动物血液游离脂肪酸（free fatty acid, FFA）显著升高，肝脏代谢发生变化。应激状态下升高的FFA是如何通过GPR120信号途径介导肝脏能量稳态调节，目前尚不清楚。内吞是GPR信号通路失敏的重要调控方式。应激状态下GPR120是否发生了內吞从而介导了肝脏代谢失衡？也未见报道。因此，本项目拟通过体内外的实验，深入研究猪应激状态下GPR120受体及其介导的下游信号通路的变化，并通过体外构建表达载体等实验，探索应激导致GPR120內吞的作用机制。研究结果对进一步认识应激导致的动物代谢紊乱，生长阻滞有重要的意义，为猪抗应激以及脂质代谢调控提供理论依据和新的靶点。

G protein-coupled receptors (GPR) 120 is a kind of long chain fatty acid receptor. In recently years researches showed that GPR120 transduce a wide array of extracellular signals and regulate body physiology including glucose metabolism, lipid deposition, inflammation reaction. It has attracted considerable attention as a potential drug target. Yet in pigs the research on the function of GPR120 is less. In our previously studies, we found that after stress, the serum free fatty acid (FFA) of pigs increased significantly. According to G protein family characteristic, when the ligands existed for a long time, the GPR will desensitization and internalization to limit GPR signaling. Many proteins including GPR kinases (GRKs), β-arrestins et al play important roles in internalization. Whether the increased FFA content after stress influenced the GPR120 function, and whether this effect is exerted via internalization are unclear. Therefore in the present study, we will treat growing pigs and primary cultured hepatocyte with dexamethasone (Dex), analysis the GPR120 and its downstream signal changes to clarify the effect of stress on porcine GPR120 function. Meanwhile we will prepare a construct of GPR120 fused with enhanced fluorescent protein (GFP) at its C-terminus for direct imaging of the localization and internalization of GPR120 by confocal microscopy. In stable transfected cells, we add different type of fatty acids and Dex to explore the possible underlying mechanism of internalization. The results will help to further understand the porcine metabolic disorder resulted by stress, and provide new clues for stress prevention and lipid regulation in pigs. Considering the homology among FFA receptors, the findings could give new insight into the investigation of other members in this family.