Chlamydia trachomatis homotypic inclusion fusion is promoted by host microtubule trafficking

Abstract

BackgroundThe developmental cycle of the obligate intracellular pathogen Chlamydia is dependant on the formation of a unique intracellular niche termed the chlamydial inclusion. The inclusion is a membrane bound vacuole derived from host cytoplasmic membrane and is modified significantly by the insertion of chlamydial proteins. A unique property of the inclusion is its propensity for homotypic fusion. The vast majority of cells infected with multiple chlamydial elementary bodies (EBs) contain only a single mature inclusion. The chlamydial protein IncA is required for fusion, however the host process involved are uncharacterized.ResultsHere, through live imaging studies, we determined that the nascent inclusions clustered tightly at the cell microtubule organizing center (MTOC) where they eventually fused to form a single inclusion. We established that factors involved in trafficking were required for efficient fusion as both disruption of the microtubule network and inhibition of microtubule trafficking reduced the efficiency of fusion. Additionally, fusion occurred at multiple sites in the cell and was delayed when the microtubule minus ends were either no longer anchored at a single MTOC or when a cell possessed multiple MTOCs.ConclusionsThe data presented demonstrates that efficient homotypic fusion requires the inclusions to be in close proximity and that this proximity is dependent on chlamydial microtubule trafficking to the minus ends of microtubules.

The late endocytic Rab39a GTPase regulates multivesicular bodies-chlamydial inclusion interaction and bacterial growth

“…2C; supplementary material Movies 2 and 3). In agreement with recent reports (Al-Zeer et al, 2014;Richards et al, 2013), our results confirm the participation of microtubules in homotypic fusion and enlargement of chlamydial inclusions (Fig. 3C).…”

“…In agreement with these findings, mutants of Rab4, Rab6, Rab11 and Rab14 only able to bind GDP do not associate with chlamydial inclusions (Capmany and Damiani, 2010;Moorhead et al, 2007;Rzomp et al, 2006). Both, chlamydial inclusion migration to the perinucleus and homotypic fusion are dependent on an intact microtubule network (Grieshaber et al, 2003;Richards et al, 2013). Furthermore, it has been recently demonstrated that microtubule depolymerization reduces inclusion growth and chlamydial replication in cells treated with nocodazole for long periods of time (Al-Zeer et al, 2014).…”

Chlamydia cell biology and pathogenesis

“…1). This facilitates interactions with nutrient-rich compartments and homotypic fusion 50 . Although some components of the dynactin complex are recruited, transport along micro tubules does not require p50 dynamitin 16,49 , which usually links cargo to microtubules.…”

A Chlamydia effector recruits CEP170 to reprogram host microtubule organization

“…An actin and intermediate filament cage is required for the integrity of mature inclusions ( Kumar and Valdivia, 2008 ), and an acto-myosin-dependent process regulates inclusion extrusion from the infected cell ( Hybiske and Stephens, 2007 ). Early Chlamydia- containing vacuoles utilize microtubules (MTs) to migrate from the cell periphery towards the MT-organizing center (MTOC) ( Richards et al, 2013 ). Src family kinases regulate the tight association of the nascent and later mature C. trachomatis inclusion with the centrosome ( Richards et al, 2013 ; Mital et al, 2010 ; Grieshaber et al, 2006 ), and disruption of this interaction forces the bacteria to enter a state of persistence ( Romano et al, 2013 ; Leonhardt et al, 2007 ).…”