昆虫肽聚糖识别蛋白研究进展

在脊椎动物和非脊椎动物中，识别非己是天生免疫反应中的第一步。肽聚糖是细菌细胞壁的必需成分，属于进化上保守的微生物表面病原相关分子模式(pathogen-associated molecular pattern, PAMP)，可以被模式识别蛋白(pattern recognition proteins, PRRs)如肽聚糖识别蛋白(peptidoglycan recognition proteins, PGRPs)识别。 在昆虫的天生免疫系统中，有些PGRPs能够利用细菌独有的肽聚糖识别入侵细菌，并将细菌入侵信号传递给下游的抗菌肽(antimicrobial peptide, AMP)合成途径，启动抗菌肽基因的转录及合成；PGRPs对肽聚糖的识别也会启动酚氧化酶原途径的激活，引起黑化反应。有些具有酰胺酶活性的PGRPs可以促进吞噬作用；有些可以抑制抗菌肽合成以减弱过度免疫反应带来的损伤。还有一些PGRPs作为效应因子直接作用于细菌将细菌杀死。本文主要从昆虫PGRPs作为识别受体(recognition receptor)、调节子(regulator)和效应因子(effector) 3个方面进行了综述，并分析了目前PGRPs研究中仍不清楚的问题和未来研究的方向。

Peptidoglycan recognition proteins (PGRPs) in insects

Peptidoglycan recognition proteins (PGRPs), a family of pattern recognition proteins, play key roles in the innate immune system against invading pathogens and parasites in vertebrates and invertebrates. Peptidoglycans (PGNs), which are conserved in most bacteria as an essential component of cell wall, are recognized by PGRPs as pathogen-associated molecular pattern (PAMP). In insects, some PGRPs function as receptors to recognize bacteria and fungi, leading to the activation of antimicrobial peptide (AMP) synthesis through IMD and Toll pathways. And this recognition also results in the activation of prophenoloxidase (PPO) cascade. Some PGRPs with amidase activity are involved in phagocytosis, and some may down-regulate AMP pathways by degradation of bacterial peptidoglycan. And some PGRPs function as effectors to kill bacteria by themselves. This review summarizes the functions of PGRPs as recognition receptor, regulator and effector in insect innate immune system and gives the directions for future study.