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Application of Genetic Techniques to Investigate Chlamydia Trachomatis Type Iii Secretion Effector Biology

Year: 2021
Type: article
Abstract: Chlamydia trachomatis is the causative agent of the most reported bacterial sexually transmitted disease in the United States. The establishment of an intracellular niche within mucosal epithelium is sufficient to drive immunopathology and disease sequela. As obligate intracellular bacteria, Chlamydia spp. have evolved numerous mechanisms for establishing an intracellular growth environment. The type III secretion system (T3SS) delivers effector proteins to the host cytosol and is essential for C. trachomatis invasion and development. The effectors TmeA, TmeB, and TarP, are all secreted during C. trachomatis invasion. TarP and TmeA have been associated with manipulation of actin networks and are essential for normal invasion levels. The functions of TarP are well established, whereas TmeA is less well characterized, and the role of TmeB is entirely unknown. Recent progress in elucidating and characterizing these effectors has been bolstered by the development of techniques enabling basic genetic tractability of C. trachomatis L2. Florescence-reported allelic exchange mutagenesis (FRAEM) couples chromosomal gene deletion with the insertion of a selection cassette encoding antibiotic resistance and green fluorescent protein (GFP); however, FRAEM-mediated deletion of Chlamydia trachomatis tmeA produces a polar effect on the downstream gene, tmeB, and negatively impacts its expression. Our laboratory has adapted FRAEM technology by employing a gfp-bla cassette flanked by loxP sites. Conditional expression of Cre recombinase in C. trachomatis tmeA null strain containing a floxed cassette resulted in the deletion of the marker cassette and restoration of tmeB expression. The work presented here utilizes the novel marker-less C. trachomatis deletion mutant to determine the importance of TmeA and TmeB during development and identify their eukaryotic host targets. We leverage chlamydial genetics and proximity labeling to provide evidence that TmeA directly targets host N-WASP to promote Arp2/3-dependent actin polymerization. Our work also shows that TmeA and TarP influence separate yet synergistic pathways to accomplish chlamydial entry, while TmeB functions antagonistically to TmeA and inhibits Arp2/3-mediated actin polymerization.
DOI: 10.13023/etd.2021.223
Language: English
Subfield: Microbiology
Open Access status: green
OpenAlex ID: W3178988134
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