改善肠道磷吸收效率对于减轻畜禽排泄物磷污染有重要意义。肠道钠磷转运系统（NaPi）是节磷减排研究的重要靶位；此系统中，NaPi-IIb主要负责磷吸收，而NaPi-III则作为“磷感受器”发挥作用。申请人用自主研制的抗体抑制NaPi-III的亚型PiT-1后，发现肉鸡肠道磷吸收效率显著提高。进一步试验显示，PiT-1可感知细胞外磷浓度信号并下调NaPi-IIb蛋白表达，但机制不明。本项目拟首先在肉鸡原代肠上皮细胞中靶向干预PiT-1，通过免疫共沉淀等技术探明PiT-1调控NaPi-IIb可能涉及的中间信号分子；然后使用抑制剂或RNAi对筛选出的中间信号分子进行干预，利用磷酸化蛋白质组学等技术明晰信号网络；最后，对PiT-1进行在体干预，探究PiT-1通过调控NaPi-IIb进而影响肉鸡肠道磷吸收的内在机制。本项目研究结果将阐明PiT-1对肠道磷吸收的限制作用，可为节磷减排技术研发提供新靶点。

Improving intestinal phosphorus absorption efficiency is of great significance for reducing phosphorus pollution from livestock and poultry excreta. The intestinal sodium-phosphorus transport system (NaPi) is an important target for the development of phosphorus-reducing strategies. Intestinal NaPi-IIb is mainly responsible for phosphorus absorption, while NaPi-III functions as "phosphorus sensor". We found that the intestinal phosphorus absorption efficiency was significantly increased in broilers when the NaPi-III subtype PiT-1 was inhibited by using an own-developed PiT-1 antibody. Further experiments showed that PiT-1 could sense extracellular phosphorus concentration signal and down-regulate the protein expression of NaPi-IIb, but the mechanism remains unknown. In this project, we will first intervene with PiT-1 in the primary intestinal epithelial cells from broilers, the PiT-1-mediated intermediate signaling molecules that regulate NaPi-IIb would be identified using techniques such as co-immunoprecipitation. Then, the selected intermediate signal molecules will be interfered by specific inhibitors or siRNAs, and the signal network will be clarified using techniques such as phosphorylation proteomics. Finally, PiT-1 will be inhibited in vivo to explore the intrinsic mechanism by which PiT-1 regulates NaPi-IIb and affects intestinal phosphorus absorption in broilers. The results of this project will clarify the role of PiT-1 in limiting broiler intestinal phosphorus absorption and provide a new target for the development of phosphorus-reducing strategies.