# Evidence for a post-invasion role of the Chlamydia trachomatis type III secreted effector TmeA in redirection of host plasma membrane-derived material

## TL;DR

This study shows that the Chlamydia effector TmeA helps redirect host cell membrane material to support the bacteria's growth inside host cells.

## Contribution

The study reveals a new post-invasion role for TmeA in redirecting host plasma membrane-derived material to the chlamydial inclusion.

## Key findings

- TmeA is secreted from mature inclusions and is necessary for inclusion size and progeny production.
- TmeA redirects plasma membrane-derived material to the inclusion via an actin-dependent pathway involving N-WASP.
- Clathrin and dynamin are required for the trafficking but not directly activated by TmeA.

## Abstract

Chlamydia spp. infect mucosal epithelia and develop within a membrane-bound vacuole termed an inclusion. Parasitism of resources from host organelles and exploitation of the actin-based cytoskeleton represent central paradigms in the establishment and maintenance of the intracellular niche created by Chlamydia spp. Manipulation of host cell biology is mediated in large part by deployment of type III secreted effector proteins. Translocated membrane-associated effector A (TmeA) is a type III secreted effector first deployed during invasion, where it is necessary for efficient entry into host cells. We provide evidence herein that TmeA also functions later during infection. De novo-synthesized TmeA is secreted from mature inclusions, and deletion of tmeA correlates with decreased inclusion size and progeny production. In addition, functional evidence supports a role of TmeA in intracellular development. We leveraged the lipophilic tracer DiI to reveal TmeA-dependent trafficking of plasma membrane-derived material to the chlamydial inclusion. The pathway was distinct from that described for sphingomyelin delivery to inclusions. Trafficking of DiI to the inclusion instead required actin polymerization and the TmeA Neural Wiskott-Aldrich syndrome protein (N-WASP) interaction domain. Ectopically expressed TmeA co-localized with internalized DiI in vesicle-like structures that also depended on the N-WASP binding domain. Clathrin and dynamin were also required but likely contribute independently of direct TmeA-mediated activation. Overall, our data provide evidence that Chlamydia repurposes TmeA to accomplish development-specific tasks and parasitizes the host surface to support intracellular growth.

Chlamydia trachomatis is a human pathogen and a prevalent agent of sexually transmitted diseases. The ability to survive and propagate within a protected intracellular niche leads directly to pathology indicative of Chlamydia-mediated disease. The reduced chlamydial genome leads to comparatively limited biosynthetic capacity, thereby necessitating parasitism of metabolites and other resources from the infected host cell. Chlamydia relies heavily on type III secreted effectors to interface with and co-opt host pathways to acquire resources. We demonstrate herein that the plasma membranes of infected cells represent a potential reservoir of resources required for optimal intracellular growth. Chlamydiae employ at least one type III secreted effector protein, translocated membrane-associated effector A (TmeA), to redirect material to the vacuole by manipulating Arp2/3-dependent actin polymerization. This pathway represents a distinct mechanism by which Chlamydia acquires resources and provides evidence for TmeA function during intracellular development.