The Chlamydia trachomatis inclusion membrane protein CT006 associates with lipid droplets in eukaryotic cells

Abstract

Chlamydia trachomatis causes genital and ocular infections in humans. This bacterial pathogen multiplies exclusively within host cells in a characteristic vacuole (inclusion) and delivers proteins such as inclusion membrane proteins (Incs) into the host cell. Here, we identified CT006 as a novel C. trachomatis protein that when expressed ectopically eukaryotic cells can associate with lipid droplets (LDs). A screen using Saccharomyces cerevisiae identified two Incs causing vacuolar protein sorting defects and seven Incs showing tropism for eukaryotic organelles. Ectopic expression in yeast and mammalian cells of genes encoding different fragments of CT006 revealed tropism for the endoplasmic reticulum and LDs. We identified a LD-targeting region within the first 88 amino acid residues of CT006, and positively charged residues important for this targeting. Comparing with the parental wild-type strain, cells infected by a newly generated C. trachomatis strain overproducing CT006 with a double hemagglutinin tag showed a slight increase in the area occupied by LDs within the inclusion region. However, we could not correlate this effect with the LD-targeting regions within CT006. We further showed that both the amino and carboxy-terminal regions of CT006, flanking the Inc-characteristic bilobed hydrophobic domain, are exposed to the host cell cytosol during C. trachomatis infection, supporting their availability to interact with host cell targets. Altogether, our data suggest that CT006 might participate in the interaction of LDs with C. trachomatis inclusions.

Whole Genome Sequencing and Comparative Genomic Analysis of Chlamydia gallinacea Field Strains Isolated from Poultry in Poland

“…To date, seven Inc subtypes (A–G), as well as a newly recognized subtype, Inc V, have been described [ 75 ]. Taking into consideration differences in nomenclature, it should be mentioned that inclusion membrane proteins are characterized by at least one bi-lobed hydrophobic motif; therefore, the in silico prediction is based on the bi-lobed hydrophobic domains occurring in these proteins [ 76 , 77 ]. In this study, four subtypes were identified by a BLAST search: Inc A (two proteins), Inc B (one protein), Inc C (one protein), and Inc V (one protein).…”

Tapping lipid droplets: A rich fat diet of intracellular bacterial pathogens

“…Some T3SS‐translocated effectors termed inclusion membrane (Inc) proteins are embedded in the inclusion membrane and play a role in the direct interaction of the inclusion membrane with the ER (Bugalhao & Mota, 2019; Derré, 2017; Dumoux et al, 2015). The C. trachomatis Inc protein CT006 associates with LDs and the ER when expressed ectopically in yeast and mammalian cells, suggesting that the protein might participate in the interaction of LDs with the inclusion (Bugalhao et al, 2022).…”