Dataset Information

Inflammasome-dependent caspase-1 activation in cervical epithelial cells stimulates growth of the intracellular pathogen Chlamydia trachomatis.

ABSTRACT: Inflammasomes have been extensively characterized in monocytes and macrophages, but not in epithelial cells, which are the preferred host cells for many pathogens. Here we show that cervical epithelial cells express a functional inflammasome. Infection of the cells by Chlamydia trachomatis leads to activation of caspase-1, through a process requiring the NOD-like receptor family member NLRP3 and the inflammasome adaptor protein ASC. Secretion of newly synthesized virulence proteins from the chlamydial vacuole through a type III secretion apparatus results in efflux of K(+) through glibenclamide-sensitive K(+) channels, which in turn stimulates production of reactive oxygen species. Elevated levels of reactive oxygen species are responsible for NLRP3-dependent caspase-1 activation in the infected cells. In monocytes and macrophages, caspase-1 is involved in processing and secretion of pro-inflammatory cytokines such as interleukin-1beta. However, in epithelial cells, which are not known to secrete large quantities of interleukin-1beta, caspase-1 has been shown previously to enhance lipid metabolism. Here we show that, in cervical epithelial cells, caspase-1 activation is required for optimal growth of the intracellular chlamydiae.

SUBMITTER: Abdul-Sater AA

PROVIDER: S-EPMC2785367 | biostudies-literature | 2009 Sep

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Inflammasome-dependent caspase-1 activation in cervical epithelial cells stimulates growth of the intracellular pathogen Chlamydia trachomatis.

Abdul-Sater Ali A AA Koo Evonne E Häcker Georg G Ojcius David M DM

The Journal of biological chemistry 20090731 39

Inflammasomes have been extensively characterized in monocytes and macrophages, but not in epithelial cells, which are the preferred host cells for many pathogens. Here we show that cervical epithelial cells express a functional inflammasome. Infection of the cells by Chlamydia trachomatis leads to activation of caspase-1, through a process requiring the NOD-like receptor family member NLRP3 and the inflammasome adaptor protein ASC. Secretion of newly synthesized virulence proteins from the chla ...[more]

PMID: 19648107

Similar Datasets

Project description:Background: Chlamydia trachomatis is a prolific human pathogen that can cause serious long-term conditions if left untreated. Recent developments in Chlamydia genetics have opened the door to conducting targeted and random mutagenesis experiments to identify gene function. In the present study, an inducible transposon mutagenesis approach was developed for C. trachomatis using a self-replicating vector to deliver the transposon-transposase cassette - a significant step towards our ultimate aim of achieving saturation mutagenesis of the Chlamydia genome. Methods: The low transformation efficiency of C. trachomatis necessitated the design of a self-replicating vector carrying the transposon mutagenesis cassette (i.e. the Himar-1 transposon containing the beta lactamase gene as well as a hyperactive transposase gene under inducible control of the tet promoter system with the addition of a riboswitch). Chlamydia transformed with this vector (pSW2-RiboA-C9Q) were induced at 24 hours post-infection. Through dual control of transcription and translation, basal expression of transposase was tightly regulated to stabilise the plasmid prior to transposition. Results: Here we present the preliminary sequencing results of transposon mutant pools of both C. trachomatis biovars, using two plasmid-free representatives: urogenital strain C. trachomatis SWFP- and the lymphogranuloma venereum isolate L2(25667R). DNA sequencing libraries were generated and analysed using Oxford Nanopore Technologies' MinION technology. This enabled 'proof of concept' for the methods as an initial low-throughput screen of mutant libraries; the next step is to employ high throughput sequencing to assess saturation mutagenesis. Conclusions: This significant advance provides an efficient method for assaying C. trachomatis gene function and will enable the identification of the essential gene set of C. trachomatis. In the long-term, the methods described herein will add to the growing knowledge of chlamydial infection biology leading to the discovery of novel drug or vaccine targets.

Project description:The innate immune system is a critical component of host defence against microbial pathogens, but effective responses require an ability to distinguish between infectious and non-infectious insult to prevent inappropriate inflammation. Using the important obligate intracellular human pathogen Chlamydia trachomatis; an organism that causes significant immunopathology, we sought to determine critical host and pathogen factors that contribute to the induction of inflammasome activation. We assayed inflammasome activation by immunoblotting and ELISA to detect IL-1β processing and LDH release to determine pyroptosis. Using primary murine bone marrow derived macrophages or human monocyte derived dendritic cells, infected with live or attenuated Chlamydia trachomatis we report that the live organism activates both canonical and non-canonical inflammasomes, but only canonical inflammasomes controlled IL-1β processing which preceded pyroptosis. NADPH oxidase deficient macrophages were permissive to Chlamydia trachomatis replication and displayed elevated type-1 interferon and inflammasome activation. Conversely, attenuated, non-replicating Chlamydia trachomatis, primed but did not activate inflammasomes and stimulated reduced type-1 interferon responses. This suggested bacterial replication or metabolism as important factors that determine interferon responses and inflammasome activation. We identified STING but not cGAS as a central mediator of interferon regulated inflammasome activation. Interestingly, exogenous delivery of a Chlamydia trachomatis metabolite and STING ligand-cyclic di-AMP, recovered inflammasome activation to attenuated bacteria in a STING dependent manner thus indicating that a bacterial metabolite is a key factor initiating inflammasome activation through STING, independent of cGAS. These data suggest a potential mechanism of how the innate immune system can distinguish between infectious and non-infectious insult and instigate appropriate immune responses that could be therapeutically targeted.

Dataset Information

Inflammasome-dependent caspase-1 activation in cervical epithelial cells stimulates growth of the intracellular pathogen Chlamydia trachomatis.

Publications

Inflammasome-dependent caspase-1 activation in cervical epithelial cells stimulates growth of the intracellular pathogen Chlamydia trachomatis.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets