Identification of Yersinia genes that influence activation of host NFκB triggered by the Type III Secretion System
Physical and Biological Sciences
Microbiology and Environmental Toxicology
Yersinia pseudotuberculosis is a human pathogen that utilizes a type III secretion
system (T3SS) to deliver six to seven effector proteins inside target host cells (YopHEMOJTK), disarming host innate immune defenses. The Y. pseudotuberculosis T3SS lacking YopHEMOJT retains the ability to activate the pro-inflammatory transcription factor NFκB in mammalian cells. We hypothesize that detection of unknown bacterial cargo injected by the T3SS activates NFκB in host cells. Since NFκB is a major regulator of the innate immune response during infection, this may be important for the ability of Yersinia to cause disease. To identify Yersinia genes required for T3SS-dependent NFκB activation, we constructed a library of 4,400 Y. pseudotuberculosis transposon mutants lacking YopHEMOJT. We infected HEK293T NFκB-luciferase reporter cells with Y. pseudotuberculosis mutants and measured bioluminescence corresponding to NFκB activity. We have screened ~2,350 mutants and identified 18 that trigger aberrant levels of host NFκB. One of the genes found in our genetic screen, SufI, may affect expression or delivery of unknown NFκB-activating T3SS cargo. SufI is thought to localize to the septal ring and is known to be a twin arginine translocation (TAT) system substrate. An additional gene identified through our genetic screen is TatB, an integral component of the TAT secretion system. We show that both sufI::Tn and tatB::Tn mutants express the T3SS at wild-type levels. As seen in the literature, we also show that sufI::Tn and tatB::Tn mutants show no defects in secretion and translocation of Yops. The Y. pseudotuberculosis TAT secretion system and SufI were previously shown to be important for virulence, yet have not been linked to the T3SS. We are currently investigating a possible relationship between TatB-dependent secretion of SufI and T3SS-dependent NFκB activation.
