The Human Centrosomal Protein CCDC146 Binds Chlamydia trachomatis Inclusion Membrane Protein CT288 and Is Recruited to the Periphery of the Chlamydia-Containing Vacuole

Abstract

Chlamydia trachomatis is an obligate intracellular human pathogen causing mainly ocular and genital infections of significant clinical and public health impact. C. trachomatis multiplies intracellularly in a membrane bound vacuole, known as inclusion. Both extracellularly and from within the inclusion, C. trachomatis uses a type III secretion system to deliver several effector proteins into the cytoplasm of host cells. A large proportion of these effectors, the inclusion membrane (Inc) proteins, are exposed to the host cell cytosol but possess a characteristic hydrophobic domain mediating their insertion in the inclusion membrane. By yeast two-hybrid, we found that C. trachomatis Inc CT288 interacts with the human centrosomal protein CCDC146 (coiled-coil domain-containing protein 146). The interaction was also detected by co-immunoprecipitation in mammalian cells either ectopically expressing CCDC146 and CT288 or ectopically expressing CCDC146 and infected by a C. trachomatis strain expressing epitope-tagged and inclusion membrane-localized CT288. In uninfected mammalian cells, ectopically expressed full-length CCDC146 (955 amino acid residues) localized at the centrosome; but in cells infected by wild-type C. trachomatis, its centrosomal localization was less evident and CCDC146 accumulated around the inclusion. Recruitment of CCDC146 to the inclusion periphery did not require intact host Golgi, microtubules or microfilaments, but was dependent on chlamydial protein synthesis. Full-length CCDC146 also accumulated at the periphery of the inclusion in cells infected by a C. trachomatis ct288 mutant; however, a C-terminal fragment of CCDC146 (residues 692–955), which interacts with CT288, showed differences in localization at the periphery of the inclusion in cells infected by wild-type or ct288 mutant C. trachomatis. This suggests a model in which chlamydial proteins other than CT288 recruit CCDC146 to the periphery of the inclusion, where the CT288-CCDC146 interaction might contribute to modulate the function of this host protein.

Got mutants? How advances in chlamydial genetics have furthered the study of effector proteins

“…A Y2H screen revealed the microdomain-localized Inc CT288 binds the centrosome protein CCDC146 (Almeida et al . 2018 ). CCDC146 localized proximal to the inclusion; however, this was only partially dependent on CT288, as CCDC146 was still recruited to a CT288 mutant (Almeida et al .…”

The multiple functions of the numerous Chlamydia trachomatis secreted proteins: the tip of the iceberg

“…Although little is known about the function of C. trachomatis IncB, its orthologue from C. psittaci can bind synaptosome-associated protein (SNAP)-associated protein (SNAPIN) and this might enable the inclusion to associate with microtubules [134]. Inc CT288 binds the centrosomal protein coiled-coil domain containing 146 (CCDC146) [135]; CCDC146 is recruited to the periphery of the inclusion but this is independent of CT288, which might however modulate the function of CCDC146 at the inclusion [135]. Inc CT850 binds dynein light chain Tctex-type 1 (DYNLT1) [132], a dynein subunit; DYNLT1 is found at inclusion microdomains and its depletion affects the association of the inclusion with centrosomes [132].…”

An endometrial organoid model ofChlamydia-epithelial and immune cell interactions

“…During infection, we observed microtubules and acetylated microtubules prominently assembled around the inclusion (Fig 2H-I). Because Chlamydia effectors, such as CT288 and IPAM, target centrosomal proteins (Almeida et al, 2018;Dumoux et al, 2015), this model can be used to explore effector functions in MT assembly during infection.…”