Proteomic analysis of Shigella virulence effectors secreted under different conditions.

There are a series of novel effector molecules secreted by the Type Three Secretion System (T3SS) of Shigella spp . reported in recent years. In this study, a proteomic approach is applied to study T3SS effectors systematically. First, proteins secreted by the S. flexneri wild-type strain after Congo Red (CR) induction are separated and identified using two-dimensional electrophoresis (2-DE) to display the relative abundance of all kinds of early effectors for the first time. Then, a gene deletion mutant of known virulence repressor (OspD1) and a gene overexpressed mutant of two known virulence activators (MxiE and IpgC) were constructed and analyzed to discover potential late effectors. Furthermore, the supernatant proteins of gene deletion mutants of two known translocators (IpaB and IpaD), which would constantly secrete effectors, were also analyzed. Among all of the secreted proteins identified in our study, IpaH1.4, IpaH_5, and IpaH_7 have not been reported before. These proteomic data of the secreted effectors will be valuable to understand the pathogenesis of S. flexneri .