Proteomic Analysis of Shigella Virulence Effectors Secreted under Different Conditions

A series of novel effector molecules secreted by the type three secretion system (T3SS) of Shigella spp. have been reported in recent years. In this study, a proteomic approach was applied to study T3SS effectors systematically. First, proteins secreted by the S. flexneri wildtype strain after Congo Red induction were separated and identified using two-dimensional electrophoresis 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 proteomics data of the secreted effectors will be valuable to understand the pathogenesis of S. flexneri.