Protein Disulfide Isomerase, a Component of the Estrogen Receptor Complex, Is Associated withChlamydia trachomatisSerovar E Attached to Human Endometrial Epithelial Cells

Abstract

Chlamydia trachomatis serovar E, the leading bacterial agent responsible for sexually transmitted diseases, is required to invade genital epithelial cells for its growth and survival, yet little is known about the adhesinreceptor interactions promoting its entry. In contrast, much has been published on the heparan sulfate receptor for binding C. trachomatis L2 elementary bodies (EBs) prior to entry into HeLa cells. Using a different experimental approach in which a biotinylated apical membrane protein receptor(s) attached to EB at 4°C was stripped off the surface of polarized HEC-1B cells and immunoprecipitated with polyclonal anti-EB antibodies, an ϳ55-kDa protein was reproducibly detected by enhanced chemiluminescence and two-dimensional gel electrophoresis. Matrix-assisted laser desorption ionization mass-spectrometry sequence analysis revealed the 55-kDa protein to be protein disulfide isomerase (PDI), a member of the estrogen receptor complex which carries out thiol-disulfide exchange reactions at infected host cell surfaces. Exposure of HEC-1B cells during EB attachment (1.5 to 2 h) to three different inhibitors of PDI reductive reactions-(i) the thiol-alkylating reagent DTNB (5,5-dithiobis[2-nitrobenzoic acid]), (ii) bacitracin, and (iii) anti-PDI antibodies-resulted in reduced chlamydial infectivity. Since (i) C. trachomatis serovar E attachment to estrogen-dominant primary human endometrial epithelial cells is dramatically enhanced and (ii) productive entry into and infectivity of EB in host cells is dependent on reduction of EB cross-linked outer membrane proteins at the host cell surface, these data provide some preliminary evidence for an intriguing new potential receptor candidate for further analysis of luminal C. trachomatis serovar E entry.

Comparison of Chlamydia trachomatis serovar L2 growth in polarized genital epithelial cells grown in three-dimensional culture with non-polarized cells

“…This intriguing difference between strains may possibly be due to the recognition of and binding to different receptor molecules on host cell surfaces that, for serovar E, may be enriched or clustered in some regions or microdomains of polarized epithelial cell apical membranes, such as lipid rafts or caveolae, proposed to be involved in serovar E but not in serovar L2 entry [19,20]. Although their role in chlamydial entry is still controversial [21][22][23], it is an interesting possibility, as many pathogens are known to interact with these membrane microdomains and that receptor molecules, such as membrane-associated estrogen receptors that locate to caveolae, have been implicated in serovar E attachment/entry [11,24]. In contrast, initial interactions of serovar L2 EB with host cell surfaces may occur via recognition of a broader range of host molecules or molecules widely represented throughout cell surfaces, such as heparan sulfate proteoglycans [25], and/or via Tarp-mediated pedestallike formation [26,27], a phenomenon shown to be more prevalent for serovar L2 than with serovar D [26] or serovar E [28].…”

A plasmid-cured Chlamydia muridarum strain displays altered plaque morphology and reduced infectivity in cell culture

“…The parental strain Nigg demonstrates a marked reduction in plaquing efficiency if applied to monolayers without centrifugation. The significance of this observation is not clear; it may reflect strain-specific or receptor-specific variations in attachment or uptake into cells as has been described for other chlamydial strains (Chen & Stephens, 1997;Davis et al, 2002;Carabeo & Hackstadt, 2001 that plasmid-deficient derivatives may be selected against under some culture conditions, and particularly when the plaque assay protocols that are used for isolation and screening do not involve centrifugation of the monolayer. We also noted that plaques formed by CM972 were one-half the diameter of the plaques of the parent strain.…”

Roles of Cellular Redox Factors in Pathogen and Toxin Entry in the Endocytic Pathways

“…Serovar E, an adhesion molecule from C. trachomatis, is known to be required for invasion of genital epithelial cells, but the host factor(s) required for the pathogen entry was not known until PDI was identified as an potential mediator [43]. PDI was detected in an earlier immunoprecipitation experiment [120]., in which a biotinylated apical membrane protein receptor attached to elementary body (EB) was stripped off the surface of HE-1B cells and immunoprecipitated with anti-EB antibodies, followed by 2D SDS-PAGE and MALDI MS analysis. During EB attachment, exposure of HEC-1B cells to three different inhibitors of PDI reductive activity (DTNB, bacitracin, and anti-PDI antibodies) resulted in reduced chlamydial infection.…”