EseE of Edwardsiella tarda Augments Secretion of Translocon Protein EseC and Expression of the escC-eseE Operon.
Edwardsiella tarda is an important Gram-negative pathogen that employs a type III secretion system (T3SS) to deliver effectors into host cells to facilitate bacterial survival and replication. These effectors are translocated into host cells through a translocon complex composed of three secreted proteins, namely, EseB, EseC, and EseD. The secretion of EseB and EseD requires a chaperone protein called EscC, whereas the secretion of EseC requires the chaperone EscA. In this study, we identified a novel protein (EseE) that also regulates the secretion of EseC. An eseE deletion mutant secreted much less EseC into supernatants, accompanied by increased EseC levels within bacterial cells. We also demonstrated that EseE interacted directly with EseC in a pulldown assay. Interestingly, EseC, EseE, and EscA were able to form a ternary complex, as revealed by pulldown and gel filtration assays. Of particular importance, the deletion of eseE resulted in decreased levels of EseB and EseD proteins in both the bacterial pellet and supernatant fraction. Furthermore, real-time PCR assays showed that EseE positively regulated the transcription of the translocon operon escC-eseE, comprising escC, eseB, escA, eseC, eseD, and eseE These effects of EseE on the translocon components/operon appeared to have a functional consequence, since the ΔeseE strain was outcompeted by wild-type E. tarda in a mixed infection in blue gourami fish. Collectively, our results demonstrate that EseE not only functions as a chaperone for EseC but also acts as a positive regulator controlling the expression of the translocon operon escC-eseE, thus contributing to the pathogenesis of E. tarda in fish.
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China.
Jia
J
Yi
College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei Province, China.
Shui Bing
SB
Xiao
College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei Province, China.
Zhi Xiong
ZX
Zeng
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China.
Jin Fang
JF
Lu
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China.
Lu Yi
LY
Liu
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China.
Zubair Ahmed
ZA
Laghari
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China.
Pin
P
Nie
Child and Family Research Institute, Vancouver, British Columbia, Canada.
Hong Bing
HB
Yu
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China xieh@ihb.ac.cn.
Hai Xia
HX
Xie
D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020609:Edwardsiella tarda / Q000502:physiology*; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D008264:Macrophages / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D051379:Mice; D018832:Molecular Chaperones / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism; D009876:Operon; D011485:Protein Binding; D021381:Protein Transport; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D014158:Transcription, Genetic; D000069296:Type III Secretion Systems; D014774:Virulence / Q000235:genetics
D001426:Bacterial Proteins; D018832:Molecular Chaperones; D046912:Multiprotein Complexes; D000069296:Type III Secretion Systems