pORF5蛋白调控PI3K/Akt/GSK3β信号通路促进沙眼衣原体生长发育机制研究

Our previous work demonstrated that pORF5 encoded by chlamydial plasmid was a secreted protein for the first time. Further study showed that pORF5 could increase the expression of HMGB1, and knocking down HMGB1 inhibited Ct growth. After enrichment analysis of pathways for differentially expressed proteins interacted with pORF5, we found that PI3K/Akt signaling pathway acted as the hub pathway. GSK3β is an intracellur downstream effector of PI3K/Akt, and TLR2 is an important receptor for HMGB1. Based on these characteristics, we hypothesize that pORF5 activates PI3K/Akt/GSK3β signal pathway mediated by HMGB1/TLR2 to promote Ct growth and development. Therefore, this project first intends to apply gene transfection, antibody blocking and RNAi to identify the effect and the mechanism of PI3K/Akt/GSK3β on Ct growth in cell and animal models. Then PCR Array technique will be used to screen the key target genes associated with PI3K/Akt/GSK3β pathway, and further to identify their function. This work will reveal the molecular mechanism for Chlamydial growth and development promoted by pORF5 protein, which not only enriches the understanding of Ct pathogenesis, but also provides a basis for its prevention and treatment.

pORF5是申请者首次证实由沙眼衣原体（Ct）质粒基因编码的分泌性蛋白。前期研究发现pORF5能上调高迁移率族蛋白1（HMGB1）的表达，敲低HMGB1表达后，Ct生长受到抑制；对pORF5相互作用的差异蛋白质组进行通路富集分析，发现PI3K/Akt为重要的中心枢纽通路；GSK3β是PI3K/Akt重要的下游因子，TLR2是HMGB1主要识别受体，据此提出pORF5介导HMGB1/TLR2激活PI3K/Akt/GSK3β通路促进Ct生长发育的假设。本研究拟采用RNAi等技术建立通路相关受体和关键分子的细胞转染模型及Ct感染动物模型，探讨PI3K/Akt/GSK3β对Ct生长发育的影响及调控机制；采用PCR Array高通量筛选该通路调控的关键靶基因，发现并确认与Ct生长发育相关的关键靶蛋白及其功能，揭示pORF5促Ct生长发育分子机制。本研究能丰富对Ct致病机制的认识，为其防治提供依据。

沙眼衣原体（Ct）是一种严格真核细胞寄生的原核细胞型微生物，具有广泛的致病谱。前期已经证实pORF5分泌性蛋白能改变宿主蛋白表达谱，差异蛋白主要富集于PI3K/Akt信号通路，在此基础上，本研究利用慢病毒载体系统构建稳定表达pORF5基因的HeLa细胞株和对照细胞株，发现内源和外源性pORF5均可激活PI3K/AKT通路，PI3K/AKT通路活化后，可促进MDM2磷酸化并发生核转位，促进p53泛素化降解抑制细胞凋亡，证实pORF5蛋白通过激活PI3K/AKT通路介导MDM2-p53相互作用轴抑制细胞凋亡；发现HMGB1干扰后，LC3、p62表达显著降低，parkin蛋白线粒体转位减少，Cyto c释放增加，线粒体膜电位下降，同时显著增加Bax表达水平、降低Bcl-2表达水平；构建了pORF5作用后PI3K/AKT通路相关差异基因表达数据库，共鉴定出223个差异mRNAs，差异基因主要富集于“Response to endoplasmic reticulum (ER) stress”“Response to unfolded protein”“Endoplasmic reticulum unfolded protein response”。进一步发现pORF5通过激活UPR活化MAPK/ERK信号通路，抑制ERK通路可抑制pORF5诱导的自噬，但不影响UPR通路的活化。提示pORF5可通过调控宿主细胞信号通路，改变宿主蛋白表达，影响宿主细胞生物学行为调控Ct生长发育。本项目可为Ct疾病的防治提供重要的实验依据。