Abstract
The actin cytoskeleton is crucially important to maintenance of the cellular structure, cell motility, and endocytosis. Accordingly, bacterial pathogens often co-opt the actin-restructuring machinery of host cells to access or create a favorable environment for their own replication. The obligate intracellular organism Chlamydia trachomatis and related species exemplify this dynamic: by inducing actin polymerization at the site of pathogen-host attachment, Chlamydiae induce their own uptake by the typically non-phagocytic epithelium they infect. The interaction of chlamydial adhesins with host surface receptors has been implicated in this effect, as has the activity of the chlamydial effector TarP (translocated actin recruitment protein). Following invasion, C. trachomatis dynamically assembles and maintains an actin-rich cage around the pathogen’s membrane-bound replicative niche, known as the chlamydial inclusion. Through further induction of actin polymerization and modulation of the actin-crosslinking protein myosin II, C. trachomatis promotes egress from the host via extrusion of the inclusion. In this review, we present the experimental findings that can inform our understanding of actin-dependent chlamydial pathogenesis, discuss lingering questions, and identify potential avenues of future study.
Highlights
The cytoskeleton is a highly dynamic structural framework composed of actin, microtubules, intermediate filaments, and septins
It has been shown that Chlamydia-directed microtubule restructuring traffics the nascent C. trachomatis inclusion to the microtubule-organizing center (MTOC)—an outcome that is presumed to enable the chlamydial scavenging of nutrients from the host [111,112]
While mechanistic study of the actin modulation by Chlamydiae is both robust and ongoing, it is important to acknowledge that actin remodeling does not occur in a vacuum, and that the effect of Chlamydia-restructured actin on the host cell has been largely unassessed
Summary
The cytoskeleton is a highly dynamic structural framework composed of actin, microtubules, intermediate filaments, and septins. ActA recruits an Arp2/3 complex to the bacterial pole, resulting in branched actin polymerization producing a comet-shaped structure that propels Listeria across the cytosol and into adjacent uninfected cells [16,17,18,19,20] This dynamic can be observed even in non-invasive bacterial pathogens. The virulence factor Tir is responsible for this effect: upon delivery into host cells by the E. coli type III secretion system (T3SS), Tir is incorporated into the plasma membrane, promoting EPEC/EHEC attachment via binding to the bacterial adhesin intimin [21,22] This clusters Tir at the site of attachment, inducing the phosphorylation of Tir’s cytosolic domain by host kinases and the subsequent recruitment of Nck [23,24]. We will summarize the field’s current understanding of actin modulation by Chlamydiae both during and after host invasion, as well as discuss potential avenues of further research
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
