Altered protein secretion of Chlamydia trachomatis in persistently infected human endocervical epithelial cells

Abstract

Chlamydia trachomatis is the most common bacterial infection of the human reproductive tract globally; however, the mechanisms underlying the adaptation of the organism to its natural target cells, human endocervical epithelial cells, are not clearly understood. To secure its intracellular niche, C. trachomatis must modulate the host cellular machinery by secreting virulence factors into the host cytosol to facilitate bacterial growth and survival. Here we used primary human endocervical epithelial cells and HeLa cells infected with C. trachomatis to examine the secretion of bacterial proteins during productive growth and persistent growth induced by ampicillin. Specifically, we observed a decrease in secretable chlamydial protease-like activity factor (CPAF) in the cytosol of host epithelial cells exposed to ampicillin with no evident reduction of CPAF product by C. trachomatis. In contrast, the expression of CopN and Tarp was downregulated, suggesting that C. trachomatis responds to ampicillin exposure by selectively altering the expression of secretable proteins. In addition, we observed a greater accumulation of outer-membrane vesicles from C. trachomatis in persistently infected cells. Taken together, these results suggest that the regulation of both gene expression and the secretion of chlamydial virulence proteins is involved in the adaptation of the bacteria to a persistent infection state in human genital epithelial cells.

Persistent Chlamydia trachomatis Infection of HeLa Cells Mediates Apoptosis Resistance through a Chlamydia Protease-Like Activity Factor-Independent Mechanism and Induces High Mobility Group Box 1 Release

“…By this mechanism CPAF also interferes with pathways involved in necrotic cell death. It has been reported that during persistent infection CPAF is not translocated into the cytoplasm of the host cell but is still present in the chlamydial inclusion (16,34). This study demonstrates a downregulation of CPAF expression by C. trachomatis during IFN-␥-induced persistence, corresponding to findings by Belland et al (5).…”

A small-molecule compound belonging to a class of 2,4-disubstituted 1,3,4-thiadiazine-5-ones inhibits intracellular growth and persistence of Chlamydia trachomatis

“…Penicillin persistence has been described as a state in which Chlamydia cells rapidly cease dividing while chromosomal and plasmid replication processes continue at the same rates, regardless of the presence or absence of penicillin (Byrne 2001). To our knowledge, only a few studies have demonstrated T3SS function during penicillin persistence (Wang et al, 2011). Wang et al (2011) found that ampicillin-induced persistent forms showed decreased expression levels of CopN and Tarp, whereas the levels and distribution of IncA in the inclusion membrane were not significantly changed.…”

“…To our knowledge, only a few studies have demonstrated T3SS function during penicillin persistence (Wang et al, 2011). Wang et al (2011) found that ampicillin-induced persistent forms showed decreased expression levels of CopN and Tarp, whereas the levels and distribution of IncA in the inclusion membrane were not significantly changed. These findings differ from those of Belland et al (2003) in an IFN-c model of C. trachomatis persistence in HeLa cells, in which tarp gene transcription was downregulated while copN transcription remained unchanged.…”

Characterization of CPAF Critical Residues and Secretion during Chlamydia trachomatis Infection

“…A chlamydial mutant deficient in type II secretion also significantly restricted CPAF secretion (10), suggesting that CPAF may get out of the outer membrane via the type II secretion apparatus, which, however, only sends CPAF into the lumen of the inclusion. Due to lack of knowledge about how CPAF reaches the host cell cytoplasm, some have questioned the validity of the detection of CPAF in the host cell cytoplasm (11) despite the fact that CPAF has been localized to the host cell cytosol consistently (3,(12)(13)(14)(15)(16)(17). Interestingly, the cytosolically localized CPAF is not colocalized with the secreted Pgp3 protein (18,19), which may suggest that CPAF and Pgp3, although both are secreted into the host cell cytoplasm, may have different host targets.…”