Open AccessS higella flexneri T 3 SS effector IpaH 4.5 modulates the host inflammatory response via interaction with NF ‐κ B p65 protein
Author(s) -
Wang Fang,
Jiang Zheng,
Li Yan,
He Xiang,
Zhao Jiangli,
Yang Xinlong,
Zhu Li,
Yin Zhitao,
Li Xuelian,
Wang Xuesong,
Liu Wei,
Shang Wei,
Yang Zhan,
Wang Simiao,
Zhen Qing,
Zhang Zhuangnian,
Yu Yaqin,
Zhong Hui,
Ye Qig,
Huang Liuyu,
Yuan Jing
Publication year - 2013
Publication title -
cellular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.542
H-Index - 138
eISSN - 1462-5822
pISSN - 1462-5814
DOI - 10.1111/cmi.12052
Subject(s) - biology , effector , shigella flexneri , ubiquitin ligase , type three secretion system , nf κb , mutant , ubiquitin , luciferase , secretion , microbiology and biotechnology , shigella , reporter gene , nfkb1 , wild type , escherichia coli , transfection , signal transduction , gene , gene expression , biochemistry , transcription factor
Summary S higella species possess a type III secretion system ( T 3 SS ), which is required for human infection and that delivers effector proteins into target host cells. Here, we show that the effector, IpaH 4.5 dampens the pro‐inflammatory cytokine response. In both the S ereny test and a murine lung infection model, the S higella Δ ipaH4.5 mutant strain caused more severe inflammatory responses and significantly induced higher pro‐inflammatory cytokine levels ( MIP ‐2 and TNF ‐α) in the lung homogenates of wild type‐infected mice. Moreover, there was a threefold decrease in bacterial colonization of the mutant compared with the WT and Δ ipaH4.5 / ipaH4.5 ‐ rescued strains. Yeast two‐hybrid screening showed that IpaH 4.5 specifically interacts with the p65 subunit of NF ‐κ B . Ten truncated versions of IpaH 4.5 and p65 spanning different regions were constructed and expressed to further map the IpaH binding sites with p65. The results revealed thatthe p65 region spanning amino acids 1–190 of p65 interacted with the IpaH 4.5/1–293 N ‐terminal region. In vitro , IpaH 4.5 displayed ubiquitin ligase activity towards ubiquitin and p65. Furthermore, the transcriptional activity of NF ‐κ B was shown to be inhibited by IpaH 4.5 utilizing a dual‐luciferase reporter gene detection system containing NF ‐κ B promoter response elements. Thus, we conclude that the IpaH 4.5 protein is an E 3 ubiquitin ligase capable of directly regulating the host inflammatory response by inhibiting the NF ‐κ B signalling pathway.