Increasing evidence indicates that endogenous enteric bacteria play a crucial role in the pathogenesis of inflammatory bowel diseases (IBDs). It is clear that gut flora contribute to the elevated levels of activated NF-???in the intestinal mucosa of IBD patients. However, it is unclear which bacterial strain and/or bacterial ?products contribute to the pathogenesis and/or maintenance of IBD. Due to the complexity of the gut flora, identification of the specific causative microbial agents in IBD remains challenging, and the search for the causative microbial agents is intense. AvrA is a pathogenic gene of certain bacteria whose encoded protein is inserted into intestinal epithelial cells through a Type III secretory pathway. In previous studies, we demonstrated that AvrA stabilizes ?-catenin, which is a negative regulator of the NF-?? pathway in epithelial cells. We hypothesize that the bacterial effector AvrA inhibits the NF-???pathway and actives the ?-catenin pathway to inhibit intestinal inflammation. In this study, I will focus on the mechanism and effects of AvrA, using both in vitro and in vivo approaches. For in vitro studies, we will colonize epithelial cells with AvrA-sufficient or -deficient bacteria strains. We will determine how the bacterial effector AvrA actually regulates NF-??/?-catenin binding and identify post-transcriptional changes in regulators of the NF-?? and ?-catenin pathways induced by AvrA (e.g., phosphorylations, ubiquitinations). We will investigate expression changes induced by AvrA in downstream targets (i.e., IL-8, c-myc, cyclin D1) of the NF-?? and???-catenin pathways. For in vivo studies, we will employ IL-10-/- mice that develop spontaneous colitis, which has been shown to require colonic bacterial colonization for full expression. These IL-10-/- mice will initially be raised in germ-free environments, and will then be mono-associated with E.coli F18 or E.coli F18AvrA+ to determine the function of AvrA in inhibiting inflammation in vivo. Elucidating the mechanisms of AvrA regulating the NF-?? and ?-catenin signaling pathways will provide new insights into how bacteria-host interactions contribute to inflammation. These studies have direct relevance to a better understanding of diseases such as inflammatory bowel diseases and infectious colitis. Lay language: This proposal is aimed at understanding the mechanism and effects of the bacterial protein AvrA in inhibiting inflammation. We will focus on the mechanism and effects of AvrA in cultured cells colonized with bacterial strains (with or without AvrA expression) and in a mouse colitis model. The information obtained from our research will provide new insights into the way bacteria-host interactions contribute to inflammation. This has direct relevance to a better understanding of diseases such as inflammatory bowel diseases and infectious colitis.
| Lu, Rong; Voigt, Robin M; Zhang, Yongguo et al. (2017) Alcohol Injury Damages Intestinal Stem Cells. Alcohol Clin Exp Res 41:727-734 |
| Lu, Rong; Zhang, Yong-Guo; Sun, Jun (2017) STAT3 activation in infection and infection-associated cancer. Mol Cell Endocrinol 451:80-87 |
| Klionsky, Daniel J (see original citation for additional authors) (2016) Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition). Autophagy 12:1-222 |
| Sun, Jun (2016) VDR/vitamin D receptor regulates autophagic activity through ATG16L1. Autophagy 12:1057-8 |
| Lu, Rong; Wu, Shaoping; Zhang, Yong-Guo et al. (2016) Salmonella Protein AvrA Activates the STAT3 Signaling Pathway in Colon Cancer. Neoplasia 18:307-316 |
| Zhang, Yong-guo; Wu, Shaoping; Lu, Rong et al. (2015) Tight junction CLDN2 gene is a direct target of the vitamin D receptor. Sci Rep 5:10642 |
| Wu, Shaoping; Yoon, Sonia; Zhang, Yong-Guo et al. (2015) Vitamin D receptor pathway is required for probiotic protection in colitis. Am J Physiol Gastrointest Liver Physiol 309:G341-9 |
| Thompson, Patricia A; Khatami, Mahin; Baglole, Carolyn J et al. (2015) Environmental immune disruptors, inflammation and cancer risk. Carcinogenesis 36 Suppl 1:S232-53 |
| Zhang, Yongguo; Wu, Shaoping; Ma, Jun et al. (2015) Bacterial protein AvrA stabilizes intestinal epithelial tight junctions via blockage of the C-Jun N-terminal kinase pathway. Tissue Barriers 3:e972849 |
| Wu, Shaoping; Zhang, Yong-Guo; Lu, Rong et al. (2015) Intestinal epithelial vitamin D receptor deletion leads to defective autophagy in colitis. Gut 64:1082-94 |
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