A path forward for the chlamydial virulence factor CPAF

Conrad, Turner; Yang, Zhangsheng; Ojcius, David M.; Zhong, Guangming

doi:10.1016/j.micinf.2013.09.008

Cited by 20 publications

(42 citation statements)

References 62 publications

(72 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The previously published controversial findings on CPAF degradation of cellular proteins in cell culture systems (32,33) motivated us to use the L2-17 strain (34) for evaluating the potential functions of CPAF in the mouse genital tracts, which led us to discover an essential role of CPAF in promoting chlamydial survival in the mouse lower genital tract. This mouse model may also allow us to further investigate the mechanisms by which CPAF aids in chlamydial survival.…”

Section: Discussionmentioning

confidence: 99%

“…The next issue is that of how CPAF promotes chlamydial survival/ascension/infectivity. It has been hypothesized that CPAF accumulated in the infected host cell cytosol at the late stage of intracellular chlamydial growth (29) may be released to confront the extracellular mucosal effectors before the intrainclusion organisms are exposed to extracellular environments during host cell lysis and chlamydial spreading (33). The fact that L2-17 was cleared within a few days after inoculation suggests that the innate immunity effectors of the lower genital tract are effective for controlling the infection and that these same effectors may be targeted by CPAF.…”

Section: Discussionmentioning

confidence: 99%

“…Although CPAF was initially discovered as a consequence of its ability to robustly degrade intracellular proteins of the infected cells (29)(30)(31), the extent to which these host targets are degraded during infection is a subject of debate (32)(33)(34)(35)(36)(37). CPAF is a unique serine protease (38)(39)(40)(41)(42) that is secreted into the host cell cytosol via a sec-dependent type II secretion pathway (34,43).…”

mentioning

confidence: 99%

See 2 more Smart Citations

The Chlamydia-Secreted Protease CPAF Promotes Chlamydial Survival in the Mouse Lower Genital Tract

et al. 2016

Self Cite

View full text Add to dashboard Cite

dDespite the extensive in vitro characterization of CPAF (chlamydial protease/proteasome-like activity factor), its role in chlamydial infection and pathogenesis remains unclear. We now report that a Chlamydia trachomatis strain deficient in expression of CPAF (L2-17) is no longer able to establish a successful infection in the mouse lower genital tract following an intravaginal inoculation. The L2-17 organisms were cleared from the mouse lower genital tract within a few days, while a CPAF-sufficient C. trachomatis strain (L2-5) survived in the lower genital tract for more than 3 weeks. However, both the L2-17 and L2-5 organisms maintained robust infection courses that lasted up to 4 weeks when they were directly delivered into the mouse upper genital tract. The CPAF-dependent chlamydial survival in the lower genital tract was confirmed in multiple strains of mice. Thus, we have demonstrated a critical role of CPAF in promoting C. trachomatis survival in the mouse lower genital tracts. It will be interesting to further investigate the mechanisms of the CPAF-dependent chlamydial pathogenicity.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

The Chlamydia-Secreted Protease CPAF Promotes Chlamydial Survival in the Mouse Lower Genital Tract

et al. 2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…CPAF has been implicated functionally in the interaction of a number of host cell substrate targets important for chlamydial pathogenesis (20). However, it was later shown that these host substrates were the result of an imprecise method that failed to inactivate the protease during sample harvest (21), which triggered discussions on the authenticity of CPAF's function (22)(23)(24).…”

mentioning

confidence: 99%

Characterization of CPAF Critical Residues and Secretion during Chlamydia trachomatis Infection

et al. 2015

Self Cite

View full text Add to dashboard Cite

CPAF (chlamydial protease-like activity factor), a Chlamydia serine protease, is activated via proximity-induced intermolecular dimerization that triggers processing and removal of an inhibitory peptide occupying the CPAF substrate-binding groove. An active CPAF is a homodimer of two identical intramolecular heterodimers, each consisting of 29-kDa N-terminal and 35-kDa C-terminal fragments. However, critical residues for CPAF intermolecular dimerization, catalytic activity, and processing were defined in cell-free systems. Complementation of a CPAF-deficient chlamydial organism with a plasmid-encoded CPAF has enabled us to characterize CPAF during infection. The transformants expressing CPAF mutated at intermolecular dimerization, catalytic, or cleavage residues still produced active CPAF, although at a lower efficiency, indicating that CPAF can tolerate more mutations inside Chlamydia-infected cells than in cell-free systems. Only by simultaneously mutating both intermolecular dimerization and catalytic residues was CPAF activation completely blocked during infection, both indicating the importance of the critical residues identified in the cell-free systems and exploring the limit of CPAF's tolerance for mutations in the intracellular environment. We further found that active CPAF was always detected in the host cell cytoplasm while nonactive CPAF was restricted to within the chlamydial inclusions, regardless of how the infected cell samples were treated. Thus, CPAF translocation into the host cell cytoplasm correlates with CPAF enzymatic activity and is not altered by sample treatment conditions. These observations have provided new evidence for CPAF activation and translocation, which should encourage continued investigation of CPAF in chlamydial pathogenesis.

show abstract

“…The most extensively studied effector protein in Chlamydia research is CPAF (chlamydial protease-like activity factor), which has been reported to degrade a broad spectrum of host cell proteins (3). However, it has been shown that the observed degradation of many previously identified CPAF substrates is an artifact of the protein isolation process (4), and thus whether CPAF actively degrades host cell proteins during the intracellular developmental cycle is a controversial subject of discussion.…”

mentioning

confidence: 99%

Structural Basis of the Proteolytic and Chaperone Activity of Chlamydia trachomatis CT441

et al. 2015

View full text Add to dashboard Cite

e Chlamydia trachomatis is the most prevalent cause of preventable blindness worldwide and a major reason for infectious infertility in females. Several bacterial factors have been implicated in the pathogenesis of C. trachomatis. Combining structural and mutational analysis, we have shown that the proteolytic function of CT441 depends on a conserved Ser/Lys/Gln catalytic triad and a functional substrate-binding site within a flexible PDZ (postsynaptic density of 95 kDa, discs large, and zonula occludens) domain. Previously, it has been suggested that CT441 is involved in modulating estrogen signaling responses of the host cell. Our results show that although in vitro CT441 exhibits proteolytic activity against SRAP1, a coactivator of estrogen receptor ␣, CT441-mediated SRAP1 degradation is not observed during the intracellular developmental cycle before host cells are lysed and infectious chlamydiae are released. Most compellingly, we have newly identified a chaperone activity of CT441, indicating a role of CT441 in prokaryotic protein quality control processes. Infections with the obligate intracellular pathogen Chlamydia trachomatis are among the most common sexually transmitted diseases worldwide, with approximately 1.5 million reported cases in the United States in 2012 (1). While most of the acute infections of the lower urogenital tract are asymptomatic and remain unrecognized by the affected people, ascending infections in females often result in severe chronic sequelae, such as pelvic inflammatory disease, ectopic pregnancy, and infertility (2). Despite its clinical relevance, many aspects of the underlying virulence mechanisms have not been elucidated so far.As for other pathogens, infectivity and the propensity to manipulate host immune responses largely depend on the repertoire of pathogenicity factors. The most extensively studied effector protein in Chlamydia research is CPAF (chlamydial protease-like activity factor), which has been reported to degrade a broad spectrum of host cell proteins (3). However, it has been shown that the observed degradation of many previously identified CPAF substrates is an artifact of the protein isolation process (4), and thus whether CPAF actively degrades host cell proteins during the intracellular developmental cycle is a controversial subject of discussion.A second chlamydial protease, designated CT441 for C. trachomatis, shares significant amino acid sequence similarity with tailspecific proteases (Tsps) from other species (e.g., 25% identity with Tsp from Escherichia coli) and was first proposed by Lad et al. to interfere with host antimicrobial and inflammatory responses (5, 6); however, in later reports, a role of CT441 and CPAF in the cleavage of NF-B during the chlamydial infection has been put into question (4, 7). Unique regions that show no similarities to any characterized domain are present at the N terminus of Tsp proteins. E. coli Tsp cleaves substrate proteins labeled with a Cterminal ssrA-encoded peptide tag (small stable RNA A) and is involved in ...

show abstract

A path forward for the chlamydial virulence factor CPAF

Cited by 20 publications

References 62 publications

The Chlamydia-Secreted Protease CPAF Promotes Chlamydial Survival in the Mouse Lower Genital Tract

The Chlamydia-Secreted Protease CPAF Promotes Chlamydial Survival in the Mouse Lower Genital Tract

Characterization of CPAF Critical Residues and Secretion during Chlamydia trachomatis Infection

Structural Basis of the Proteolytic and Chaperone Activity of Chlamydia trachomatis CT441

Contact Info

Product

Resources

About