A molecular switch of the type III secretion system in Chlamydia trachomatis The obligate intracellular bacterium C. trachomatis is the causative agent of the most common sexually transmitted disease worldwide and represents a significant public health burden. The severe sequelae of genital chlamydial infections in women include pelvic inflammatory disease, ectopic pregnancy and tubal infertility. A key virulence mechanism of C. trachomatis is the type III secretion system (T3SS) that directly delivers protein effectors into the host cell cytosol to subvert host immunity and enables bacterial survival in hosts. The objective of this project is to study the mechanism by which C. trachomatis controls type III secretion and gene expression, contributing to disease pathogenesis. We hypothesize that T3SS activity is regulated and coupled to gene transcription during C. trachomatis infection by a molecular switch, consisting of CT663 and its protein partners. This hypothesis is strongly supported by our novel finding that chlamydial CT663 is a bi-functional protein acting as both a transcription regulator that interacts with RNA polymerase containing ? 66 and a T3SS chaperone for CopN, which is a regulator as well as an effector of the T3SS.
Our specific aims are:
Aim 1. To test the hypothesis that CT663 forms a protein complex necessary for type III secretion activity. We will characterize the dynamic interactions of CT663 and its partners, and how these interactions impact the secretion activity using quantitative assays for protein-protein interactions, immunodetection, and an enteropathogenic Escherichia coli (EPEC) system.
Aim 2. To test the hypothesis that CT663 differentially regulates the gene transcription.
This aim willbe achieved using our established transcription assays with reconstituted ?66RNA polymerase in vitro and in E. coli. These studies will uncover how T3SS activity affects gene expression during C. trachomatis infection and vice versa. This project will provide important insights into how C. trachomatis utilizes T3SS to survive in an intracellular niche by coordinating the regulatory events of the T3SS and gene expression during infection. Our research will significantly expand current knowledge of the C. trachomatis infection process and contribute to the identification of potential drug targets for new therapies that could significantly reduce the public health burden caused by C. trachomatis infection.

Public Health Relevance

Our research will significantly expand current knowledge of the Chlamydia trachomatis infection process and contribute to the identification of potential drug targets for new therapies that could significantly reduce the public health burden caused by Chlamydia trachomatis infection.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
High Priority, Short Term Project Award (R56)
Project #
1R56AI093565-01A1
Application #
8509139
Study Section
Bacterial Pathogenesis Study Section (BACP)
Program Officer
Hiltke, Thomas J
Project Start
2012-08-01
Project End
2014-07-31
Budget Start
2012-08-01
Budget End
2014-07-31
Support Year
1
Fiscal Year
2012
Total Cost
$355,424
Indirect Cost
$105,424
Name
Louisiana State Univ Hsc New Orleans
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
782627814
City
New Orleans
State
LA
Country
United States
Zip Code
70112
Cong, Yanguang; Gao, Leiqiong; Zhang, Yan et al. (2016) Quantifying promoter activity during the developmental cycle of Chlamydia trachomatis. Sci Rep 6:27244
Hua, Ziyu; Frohlich, Kyla M; Zhang, Yan et al. (2015) Andrographolide inhibits intracellular Chlamydia trachomatis multiplication and reduces secretion of proinflammatory mediators produced by human epithelial cells. Pathog Dis 73:1-11
Shen, Li; Macnaughtan, Megan A; Frohlich, Kyla M et al. (2015) Multipart Chaperone-Effector Recognition in the Type III Secretion System of Chlamydia trachomatis. J Biol Chem 290:28141-55
Frohlich, Kyla; Hua, Ziyu; Wang, Jin et al. (2012) Isolation of Chlamydia trachomatis and membrane vesicles derived from host and bacteria. J Microbiol Methods 91:222-30