微孢子虫（Microsporidia）是一类专性细胞内寄生的单细胞真菌, 可感染昆虫、鱼类和人类等，家蚕微粒子虫是第一种被鉴定的微孢子虫。微孢子虫侵染宿主的机制在自然界十分独特，是通过极管弹出方式刺入宿主肠道细胞，将原生质体沿极管注入宿主细胞内，完成感染，但极管弹出过程的分子调控机制至今未得到解析，是微孢子虫学界的重大科学问题。我们前期研究发现，家蚕微粒子虫类枯草杆菌蛋白酶1（NbSLP1）恰恰定位于孢子的极管弹出位置，其抑制剂PMSF可显著抑制微孢子虫极管弹出率，其潜在的底物孢壁蛋白16（SWP16）也位于极管弹出的开口位置，我们推测NbSLP1可能通过水解SWP16，打开了极管弹出的孔道。本项目拟通过底物鉴定、蛋白互作、结构解析等方法，重点鉴定NbSLP1底物以及该底物蛋白的互作网络，验证以SLP1水解底物蛋白为核心的极管弹出调控假说，本研究对阐明微孢子虫的侵染机制具有重要意义。

Microsporidia are a large group of eukaryotic, obligate intracellular fungi, which can infect various hosts including insects，fish and human beings. The invasion mechanism of Microsporidia is very unique in nature. Under appropriate environmental stimulation in intestine, the spores’ polar tube rapidly discharges out of the spore, pierces into the intestine cell, and serves as a conduit for sporoplasm passage into the host cell. However, the regulation mechanism of polar tube extrusion remains to be determined as one of the most important scientific questions in Microsporidia. Recently, we found that subtilisin-like protease 1 of Nosema bombycis (NbSLP1), the pathogen of silkworm pebrine disease, located at the budding position of germinated spores, and the germination rate could be inhibited by subtilisin inhibitor PMSF significantly. Coincidentally, the NbSLP1 potential substrate anchoring disk complex protein SWP16 just locates at the budding position. According to our findings, we hypothesized that NbSLP1 hydrolyzing the anchoring disk complex protein contributes to the hole formation on the apical of the spore for the polar tube extrusion in the germination process. Through the substrate screening, protein interaction and three dimensional analysis, we mainly focus on the identification of the substrates of NbSLP1 in N. bombycis, and clarification of the roles of NbSLP1 in regulating the polar tube extrusion process, our work will establish the foundation to discover invasion mechanisms of Microsporidia, the scientific question for more than one hundred years.