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Coxiella burnetii Nine Mile II proteins modulate gene expression of monocytic host cells during infection.

ABSTRACT: Coxiella burnetii is an intracellular bacterial pathogen that causes acute and chronic disease in humans. Bacterial replication occurs within enlarged parasitophorous vacuoles (PV) of eukaryotic cells, the biogenesis and maintenance of which is dependent on C. burnetii protein synthesis. These observations suggest that C. burnetii actively subverts host cell processes, however little is known about the cellular biology mechanisms manipulated by the pathogen during infection. Here, we examined host cell gene expression changes specifically induced by C. burnetii proteins during infection.We have identified 36 host cell genes that are specifically regulated when de novo C. burnetii protein synthesis occurs during infection using comparative microarray analysis. Two parallel sets of infected and uninfected THP-1 cells were grown for 48 h followed by the addition of chloramphenicol (CAM) to 10 ?g/ml in one set. Total RNA was harvested at 72 hpi from all conditions, and microarrays performed using Phalanx Human OneArray slides. A total of 784 (mock treated) and 901 (CAM treated) THP-1 genes were up or down regulated ?2 fold in the C. burnetii infected vs. uninfected cell sets, respectively. Comparisons between the complementary data sets (using >0 fold), eliminated the common gene expression changes. A stringent comparison (?2 fold) between the separate microarrays revealed 36 host cell genes modulated by C. burnetii protein synthesis. Ontological analysis of these genes identified the innate immune response, cell death and proliferation, vesicle trafficking and development, lipid homeostasis, and cytoskeletal organization as predominant cellular functions modulated by C. burnetii protein synthesis.Collectively, these data indicate that C. burnetii proteins actively regulate the expression of specific host cell genes and pathways. This is in addition to host cell genes that respond to the presence of the pathogen whether or not it is actively synthesizing proteins. These findings indicate that C. burnetii modulates the host cell gene expression to avoid the immune response, preserve the host cell from death, and direct the development and maintenance of a replicative PV by controlling vesicle formation and trafficking within the host cell during infection.

SUBMITTER: Mahapatra S

PROVIDER: S-EPMC2954873 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Coxiella burnetii Nine Mile II proteins modulate gene expression of monocytic host cells during infection.

Mahapatra Saugata S Ayoubi Patricia P Shaw Edward I EI

BMC microbiology 20100920

<h4>Background</h4>Coxiella burnetii is an intracellular bacterial pathogen that causes acute and chronic disease in humans. Bacterial replication occurs within enlarged parasitophorous vacuoles (PV) of eukaryotic cells, the biogenesis and maintenance of which is dependent on C. burnetii protein synthesis. These observations suggest that C. burnetii actively subverts host cell processes, however little is known about the cellular biology mechanisms manipulated by the pathogen during infection. H ...[more]

PMID: 20854687

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Project description:UNLABELLED:Coxiella burnetii is an intracellular pathogen that replicates within a lysosome-like vacuole. A Dot/Icm type IVB secretion system is used by C. burnetii to translocate effector proteins into the host cytosol that likely modulate host factor function. To identify host determinants required for C. burnetii intracellular growth, a genome-wide screen was performed using gene silencing by small interfering RNA (siRNA). Replication of C. burnetii was measured by immunofluorescence microscopy in siRNA-transfected HeLa cells. Newly identified host factors included components of the retromer complex, which mediates cargo cycling between the endocytic pathway and the Golgi apparatus. Reducing the levels of the retromer cargo-adapter VPS26-VPS29-VPS35 complex or retromer-associated sorting nexins abrogated C. burnetii replication. Several genes, when silenced, resulted in enlarged vacuoles or an increased number of vacuoles within C. burnetii-infected cells. Silencing of the STX17 gene encoding syntaxin-17 resulted in a striking defect in homotypic fusion of vacuoles containing C. burnetii, suggesting a role for syntaxin-17 in regulating this process. Lastly, silencing host genes needed for C. burnetii replication correlated with defects in the translocation of Dot/Icm effectors, whereas, silencing of genes that affected vacuole morphology, but did not impact replication, did not affect Dot/Icm translocation. These data demonstrate that C. burnetii vacuole maturation is important for creating a niche that permits Dot/Icm function. Thus, genome-wide screening has revealed host determinants involved in sequential events that occur during C. burnetii infection as defined by bacterial uptake, vacuole transport and acidification, activation of the Dot/Icm system, homotypic fusion of vacuoles, and intracellular replication. IMPORTANCE:Q fever in humans is caused by the bacterium Coxiella burnetii. Infection with C. burnetii is marked by its unique ability to replicate within a large vacuolar compartment inside cells that resembles the harsh, acidic environment of a lysosome. Central to its pathogenesis is the delivery of bacterial effector proteins into the host cell cytosol by a Dot/Icm type IVB secretion system. These proteins can interact with and manipulate host factors, thereby leading to creation and maintenance of the vacuole that the bacteria grow within. Using high-throughput genome-wide screening in human cells, we identified host factors important for several facets of C. burnetii infection, including vacuole transport and membrane fusion events that promote vacuole expansion. In addition, we show that maturation of the C. burnetii vacuole is necessary for creating an environment permissive for the Dot/Icm delivery of bacterial effector proteins into the host cytosol.

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Coxiella burnetii Nine Mile II proteins modulate gene expression of monocytic host cells during infection.

Publications

Coxiella burnetii Nine Mile II proteins modulate gene expression of monocytic host cells during infection.

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