The Chlamydia trachomatis Extrusion Exit Mechanism Is Regulated by Host Abscission Proteins

Abstract

The cellular exit strategies of intracellular pathogens have a direct impact on microbial dissemination, transmission, and engagement of immune responses of the host. Chlamydia exit their host via a budding mechanism called extrusion, which offers protective benefits to Chlamydia as they navigate their extracellular environment. Many intracellular pathogens co-opt cellular abscission machinery to facilitate cell exit, which is utilized to perform scission of two newly formed daughter cells following mitosis. Similar to viral budding exit strategies, we hypothesize that an abscission-like mechanism is required to physically sever the chlamydial extrusion from the host cell, co-opting the membrane fission activities of the endosomal sorting complex required for transport (ESCRT) family of proteins that are necessary for cellular scission events, including abscission. To test this, C. trachomatis L2-infected HeLa cells were depleted of key abscission machinery proteins charged multivesicle body protein 4b (CHMP4B), ALIX, centrosome protein 55 (CEP55), or vacuolar protein sorting-associated protein 4A (VPS4A), using RNA interference (RNAi). Over 50% reduction in extrusion formation was achieved by depletion of CHMP4B, VPS4A, and ALIX, but no effect on extrusion was observed with CEP55 depletion. These results demonstrate a role for abscission machinery in C. trachomatis extrusion from the host cell, with ALIX, VPS4A and CHMP4B playing key functional roles in optimal extrusion release.

The Type III Secretion Effector CteG Mediates Host Cell Lytic Exit of Chlamydia trachomatis

“…This is the first chlamydial T3S effector involved in this process, thus filling the gap of the previously proposed link between the C. trachomatis virulence plasmid and its T3S system ( Yang et al., 2015 ) in mediating this essential step of the chlamydial infectious cycle. Our work, together with previous related studies ( Hybiske and Stephens, 2007 ; Yang et al., 2015 ), indicates that, as chlamydial egress by extrusion of the inclusion ( Lutter et al., 2013 ; Nguyen et al., 2018 ; Shaw et al., 2018 ; Zuck and Hybiske, 2019 ), C. trachomatis lytic exit involves different chlamydial players [CteG, Pgp4, at least one of the several Pgp4-regulated genes ( Song et al., 2013 ; Patton et al., 2018 ), and CPAF], likely host cell factors and different layers of regulation.…”

Robust Heat Shock Response in Chlamydia Lacking a Typical Heat Shock Sigma Factor

“…Some ESCRT complexes are required for the multivesicular body (MVB) pathway and cytokinesis ( Babst, 2011 ; Schmidt and Teis, 2012 ). Others may be involved in C. trachomatis extrusion exit ( Zuck and Hybiske, 2019 ). Although previous research showed that the host proteins interacting with DUF582 are dispensable for C. trachomatis infection and growth, it is possible that they play more prominent roles for chlamydial survival under stress conditions.…”

“…Some ESCRT complexes are required for the multivesicular body (MVB) pathway and cytokinesis (Babst, 2011;Schmidt and Teis, 2012). Others may be involved in C. trachomatis extrusion exit (Zuck and Hybiske, 2019).…”

Chlamydia trachomatisCell-to-Cell Spread through Tunneling Nanotubes

“…Two dissemination strategies for chlamydia are well-characterized in the literature ( 44 ): (i) the expulsion of EBs through host cell lysis and (ii) the extrusion of bacteria while maintaining host cell integrity. In the case of extrusions, a vacuolar structure pinches off from the cell surface, which contains a layer of cytoplasm sandwiched between the outer plasma membrane-derived lipid bilayer and the inner inclusion-derived membrane, the latter of which encases the bacteria ( 45 , 46 ). The outer membrane frequently displays phosphatidylserine, which facilitates the uptake of the organisms by professional phagocytes ( 47 ).…”