Chlamydia trachomatis Coordinates Distinct Cytoskeletal Elements to Regulate Its Virulence
Abstract
The cytoskeleton is essential for cellular function and is comprised mainly of actin and microtubules. These structures dynamically rearrange throughout the cell to regulate cell motility, cell shape, cell division, transport of intracellular cargo and positioning of host organelles. Thus, the cytoskeleton is a prime target for pathogenic control. Intracellular pathogens, such as Chlamydia, readily hijack actin and microtubules to infect cells, evade anti-bacterial defenses, and disseminate within the host. Chlamydia trachomatis is an obligate intracellular bacterium that replicates within a membrane-bound vacuole, termed the inclusion. Chlamydia supports the inclusion, in part, by secreting bacterial effectors directly into the inclusion membrane. Notably, the function of many inclusion membrane proteins, or Incs, is unknown.Chlamydia trachomatis weaves an extensive network of kinetically and functionally distinct stable microtubules and actin filaments into scaffold-like structures around the inclusion. Stable microtubule and actin scaffolds enable interactions with host organelles and enhance inclusion stability, respectively. We and others have shown that the Inc for actin assembly (InaC, also known as CT813/CTL0184) is required to form stable microtubule and actin scaffolds. Moreover, stable microtubule and actin scaffold formation also require the host small GTPases ARF1/4 and RhoA, respectively. While microtubule and actin scaffolds are critical for Chlamydia pathogenicity, the molecular mechanisms that control these kinetically and functionally distinct structures are poorly understood.This dissertation will test the hypothesis that InaC utilizes specific bioactive domains to hijack host effectors to coordinate the formation of stable microtubule and actin scaffolds to regulate Chlamydia fitness, which will be assessed through three aims.1)Determine whether InaC interacts with host effectors to coordinate the kinetics of stable microtubule and actin scaffold formation. Here, we identify the molecular mechanisms by which InaC coordinates the recruitment and activation of host effectors to spatiotemporally regulate cytoskeletal scaffold formation. (2) Identify how InaC regulates actin scaffold dynamics. This section elucidates how InaC regulates inclusion stability through crosslinking and stabilization of actin scaffolds. 3) Determine whether InaC encodes independent bioactive protein domains to control stable microtubule versus actin scaffolds. This final aim utilizes biochemical approaches and genetic manipulation of Chlamydia to identify the potential bioactive domains of InaC.Ultimately, these results highlight InaC as a master regulator of the host cytoskeleton. A more comprehensive understanding of how host and bacterial effectors co-opt the cytoskeleton is critical to elucidating conserved strategies utilized by other pathogenic bacteria. Furthermore, this work could help identify novel host targets or anti- bacterial therapeutics to treat infectious diseases.
Subject Area
Microbiology|Cellular biology|Biochemistry|Pathology
Recommended Citation
Haines, Adam, "Chlamydia trachomatis Coordinates Distinct Cytoskeletal Elements to Regulate Its Virulence" (2023). ProQuest ETD Collection - Thomas Jefferson University. AAI30689457.
https://jdc.jefferson.edu/dissertations/AAI30689457
