CteG is a Chlamydia trachomatis effector protein that associates with the Golgi complex of infected host cells

Sara V Pais,João Paulo Gomes,Vítor Borges,Inês S Pereira,Charlotte E Key,Luís Jaime Mota,Derek J Fisher

doi:10.1038/s41598-019-42647-3

Abstract

Chlamydia trachomatis is a bacterial pathogen causing ocular and genital infections in humans. C. trachomatis multiplies exclusively inside host cells within a characteristic vacuole, from where it manipulates host cells by injecting them with type III secretion effector proteins. Here, we identified CteG as the first C. trachomatiseffector associated with the Golgi. For this, C. trachomatis strains expressing candidate effectors fused to a double hemagglutinin (2HA) tag were constructed. Then, among these strains, immunofluorescence microscopy revealed that CteG-2HA was delivered into the cytoplasm of infected cells. Between 16–20 h post-infection, CteG-2HA mostly associated with the Golgi; however, CteG-2HA also appeared at the host cell plasma membrane, and at 30 or 40 h post-infection this was its predominant localization. This change in the main localization of CteG-2HA was independent of intact microfilaments or microtubules. Ectopic expression of different regions of CteG (656 amino acid residues) in uninfected cells revealed that its first 100 residues contain a Golgi targeting region. Although a C. trachomatis cteG mutant did not display a defect in intracellular multiplication, CteG induced a vacuolar protein sorting defect when expressed in Saccharomyces cerevisiae. This suggested that CteG might function by subverting host cell vesicular transport.

Highlights

Chlamydia trachomatis serovars are obligate intracellular bacterial pathogens usually causing ocular and genital infections that affect millions of people worldwide and can lead to blindness and sterility
To test if the candidate chlamydial T3S substrates CT053, CT082, CT105, CT429, and CT84927,28 can be transported by Chlamydia into the cytoplasm of host cells, C. trachomatis strain L2/434 was transformed with plasmids encoding these proteins with a double hemagglutinin (2HA) epitope tag at their C-termini
Protein production was confirmed by immunoblotting of extracts of HeLa cells infected for 40 h with C. trachomatis strains harboring plasmids encoding CT053-2HA, CT082-2HA (60 kDa), CT105-2HA (68 kDa), CT4292HA (39 kDa), or CT849-2HA (18 kDa) (Figs 1A and S1)

Summary

Introduction

Chlamydia trachomatis serovars are obligate intracellular bacterial pathogens usually causing ocular and genital infections that affect millions of people worldwide and can lead to blindness and sterility. In Chlamydia, T3S effectors include the Inc proteins, characterized by a bilobed hydrophobic motif mediating their insertion into the inclusion membrane[9,10]. The identification of Chlamydia effectors without the bilobed hydrophobic motif is normally more challenging because their primary structure normally lacks other obvious distinguishable features. Several of these non-Inc C. trachomatis T3S effectors (e.g., TarP, TepP, CT694/TmeA) have been identified and shown to modulate chlamydial invasion and diverse host cell functions[4,11,12,13,14,15]. Using Saccharomyces cerevisae as model, we show that CT105 can modulate eukaryotic vesicular trafficking

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