Characterizing interactions between Chlamydia trachomatis type III secreted effector TmeA and modulators of the actin cytoskeleton during early host cell infection

Chlamydia trachomatis (C.t.) is a bacterial pathogen that represents a significant health burden in the United States and worldwide. C.t. causes an eye infection, trachoma, and the sexually transmitted infections (STIs) chlamydia and lymphogranuloma venerium. Trachoma is the leading cause of blindness worldwide, while the STIs can lead to severe complications including cancer and infertility.

C.t. is an obligate intracellular bacterium, meaning that it must be able to invade human cells to replicate and cause disease. This work identifies one method C.t. uses to invade host cells, centered around a C.t. protein, TmeA. TmeA is injected into human cells upon C.t. binding to the outer membrane and recruits and activates human proteins, driving the human cell to generate structures to engulf the bacterium. We identified two human proteins, N-WASP and TOCA-1, that are directly bound by TmeA during early stages of infection. TmeA recruits and binds N-WASP at N-WASP’s natural activation site, leading to activation of the downstream human Arp2/3 complex. TmeA additionally binds TOCA-1, and both TOCA-1 and N-WASP play a role in generation of pedestal-like structures prior to bacterial invasion of the host cell. Ultimately, N-WASP and Arp2/3 complex activation by TmeA drive engulfment of C.t.. In addition to these proteins, we used a CRISPR screen to identify additional candidates that may be similarly exploited by C.t. during the infection of human cells.

Collectively, this work provides new insight into how Chlamydia trachomatis invades human cells and highlights a critical step in its pathogenic developmental cycle.