The Effect of Chlamydia trachomatis Infection on the Host Cell Cytoskeleton and Membrane Compartments

Abstract

Human epithelial cells and the McCoy cell line were infected with Chlamydia trachomatis, serotype E. The organization of the cytoplasm was then studied with probes which stained cytoskeletal components and membrane compartments. The major actin-containing stress fibre bundles were not associated with inclusions due to the peri-basal and peri-apical location of these bundles within the host cell. The cytokeratin network was distorted by the presence of inclusions so that a common basket of these intermediate filaments surrounded both nucleus and peri-nuclear inclusions. The microtubule network was similarly distorted, but the nucleus and inclusion were surrounded by separate rather than joint baskets of tubules. After reversible depolymerization by nocadazole the microtubules in amniotic epithelial cells began to reassemble at the peri-nuclear microtubule-organizing centre, so that independent microtubule networks were rapidly regenerated around the nucleus and inclusion. Mitochondria of amniotic epithelial cells were vitally stained with the fluorescent probe DiOC6 (3,3'-dihexyloxacarbocyanine iodide) after 48 h of infection and found to be widely distributed throughout the host cytoplasm. When the morphology of the Golgi complex was examined with C6-NBD-ceramide (N-[7-(4-nitrobenzo-2-oxa-1,3-diazole)] aminocaproyl sphingosine) the main cisternae were retained in a juxta-nuclear position, although scattered stained structures were also present close to the cytoplasmic surface of the inclusion. These results demonstrate that the peri-nuclear position of inclusions is determined by the configuration of the cytoskeleton, and that normal host-cell architecture is maintained during infection, albeit in a distorted form.

Manipulation of Host Cholesterol by Obligate Intracellular Bacteria

“…Inc222 and Inc850 stably interact with one another and may form a complex within the inclusion microdomains. While the functions of IncB, Inc101, and Inc222 are unknown, Inc850 may play a critical role during inclusion development by mediating microtubule-dependent trafficking of the nascent chlamydial inclusion to the perinuclear microtubule organizing center (MTOC) (Campbell et al, 1989a,b; Grieshaber et al, 2003). Inc850 was found to bind dynein light chain, DYNLT1, thus facilitating interactions between the inclusion and the host microtubule network that are required for trafficking to the MTOC (Mital et al, 2010, 2015).…”

Caveolin-2 associates with intracellular chlamydial inclusions independently of caveolin-1

“…Instead, the inclusions provide an intracellular niche in which the pathogen can survive and complete its developmental cycle. The initial pathogen-containing endocytic vacuoles co-associate with microtubules, and dynein, and traffic to a perinuclear region, ultimately residing at the microtubule organizing center and in close proximity to the Golgi [4,5]. Here, they intercept exocytic vesicles of the biosynthetic pathway that are derived from the Golgi and continue their developmental cycle [6-9].…”

Contrasting Lifestyles Within the Host Cell

“…Mital, et al identified cholesterol-rich microdomains on the inclusion membrane that appear to serve as platforms for signaling through Src-family kinases and interaction with centrosomes and dynein (70). Once at the MTOC, the growing inclusion requires a dynamic cytoskeletal scaffold for stabilization (55, 71). The structural integrity maintained by this framework may prevent leakage of inclusion contents into the host cytosol, which might otherwise alert the host cell's innate immune system.…”