Chlamydia trachomatis pORF5 protein inhibits apoptosis through activating PI3K-Akt pathway / 中国免疫学杂志

ABSTRACT

Objective:To study the relationship between apoptosis and the pORF5 protein of Chlamydia trachomatis,and further to explore its molecular mechanisms,which could lay a foundation for chlamydial pathogenic mechanisms.Methods:pGEX-6p/pORF5 recombinant expression vector was transformed to XL1-blue E.Coli to express GST-pORF5 fusion protein,and GST-pORF5 fusion protein was purified with Glutathione Sepharose 4B Beads,and cleaved to get pORF5 protein without GST tag by PreScission protease.The pORF5 protein was used to stimulate HeLa cells at different concentrations,then Western blot was used to evaluate the ex-pression of Bax,Bcl-2 and phosphorylation of PI3K/Akt at different time points,Hoechst staining and Flow cytometry were applied to measure the apoptosis of HeLa cells.Before treated with pORF5 protein for 24 h,HeLa cells were pretreated with PI3K inhibitor LY294002 for 1 h,the expression of Bax,Bcl-2 and the phosphorylation of Akt were evaluated by Western blot,apoptosis rates were also determined.Results:The pORF5 protein changed the expression of Bax and Bcl-2 in dose-and time-dependent manners,pORF5 increased the expression of Bcl-2 and decreased the expression of Bax at the concentration of 10 μg/ml,and there was obvious change at concentration of 15 μg/ml for 24 h.The apoptosis rates of pORF5 treated group were reduced by 27.3% and 8.4% respectively when compared with TNF-α treated group(P<0.01) and untreated group (P<0.05).Akt was phosphorylated after stimulated with pORF5 protein for 15 min,and reached its peak at 30 min.PI3K/Akt inhibitor led to the decrease of the expression of Bcl-2 and phosphorylation of Akt and increase of the expression of Bax,furthermore,PI3K/Akt inhibitor reversed pORF5-mediated anti-apoptosis, the apoptosis rate in LY294002 treated group was increased by 13.0%,when compared with the control group(P<0.01).Conclusion:pORF5 protein could inhibit apoptosis through activating PI3K/Akt signal pathway by induction of Bcl-2 and suppression of Bax.