Dataset Information

Macrophage-induced genes of Legionella pneumophila: protection from reactive intermediates and solute imbalance during intracellular growth.

ABSTRACT: A promoter-probe strategy was devised to identify genes specifically expressed by Legionella pneumophila during growth within the macrophage. Random fragments from the L. pneumophila chromosome were inserted upstream of a promoterless phage T4 td gene, and fragments that led to complementation of thymine auxotrophy during intracellular growth of the bacterium were identified. Two different selection strategies were employed to eliminate promoters that were also active during extracellular growth of the bacterium. Some of these genes were identified independently by using both of the selection strategies. The factors identified include orthologs of efflux-mediated resistance determinants and transporters, a transporter involved in protection from osmotic stress, a stress response GTP-binding protein, a response regulator, a sensor kinase, and two systems that increase the reducing potential of the bacterium, one of which encodes the L. pneumophila ortholog of ahpC. Five of the clones analyzed here were fusions to promoters that were closely linked to genes encoding three-component chemiosmotic efflux pumps that export heavy metals or toxic organic compounds. Analysis of ahpC gene expression indicates that levels increased at least sevenfold during intracellular growth of the bacterium. Inactivation of several of the genes at their chromosomal loci had no effect on the intracellular growth rate of L. pneumophila in cultured macrophages. This suggests that a number of genes with increased expression during intracellular growth may be part of redundant systems that allow survival and growth under the conditions encountered within host cells.

SUBMITTER: Rankin S

PROVIDER: S-EPMC128052 | biostudies-literature | 2002 Jul

REPOSITORIES: biostudies-literature

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Macrophage-induced genes of Legionella pneumophila: protection from reactive intermediates and solute imbalance during intracellular growth.

Rankin Susannah S Li Zhiru Z Isberg Ralph R RR

Infection and immunity 20020701 7

A promoter-probe strategy was devised to identify genes specifically expressed by Legionella pneumophila during growth within the macrophage. Random fragments from the L. pneumophila chromosome were inserted upstream of a promoterless phage T4 td gene, and fragments that led to complementation of thymine auxotrophy during intracellular growth of the bacterium were identified. Two different selection strategies were employed to eliminate promoters that were also active during extracellular growth ...[more]

PMID: 12065505

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Project description:Vacuolar bacterial pathogens are sheltered within unique membrane-bound organelles that expand over time to support bacterial replication. These compartments sequester bacterial molecules away from host cytosolic immunosurveillance pathways that induce antimicrobial responses. The mechanisms by which the human pulmonary pathogen Legionella pneumophila maintains niche homeostasis are poorly understood. We uncovered that the Legionella-containing vacuole (LCV) required a sustained supply of host lipids during expansion. Lipids shortage resulted in LCV rupture and initiation of a host cell death response, whereas excess of host lipids increased LCVs size and housing capacity. We found that lipids uptake from serum and de novo lipogenesis are distinct redundant supply mechanisms for membrane biogenesis in Legionella-infected macrophages. During infection, the metabolic checkpoint kinase Mechanistic Target of Rapamycin (MTOR) controlled lipogenesis through the Serum Response Element Binding Protein 1 and 2 (SREBP1/2) transcription factors. In Legionella-infected macrophages a host-driven response that required the Toll-like receptors (TLRs) adaptor protein Myeloid differentiation primary response gene 88 (Myd88) dampened MTOR signaling which in turn destabilized LCVs under serum starvation. Inactivation of the host MTOR-suppression pathway revealed that L. pneumophila sustained MTOR signaling throughout its intracellular infection cycle by a process that required the upstream regulator Phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) and one or more Dot/Icm effector proteins. Legionella-sustained MTOR signaling facilitated LCV expansion and inhibition of the PI3K-MTOR-SREPB1/2 axis through pharmacological or genetic interference or by activation of the host MTOR-suppression response destabilized expanding LCVs, which in turn triggered cell death of infected macrophages. Our work identified a host metabolic requirement for LCV homeostasis and demonstrated that L. pneumophila has evolved to manipulate MTOR-dependent lipogenesis for optimal intracellular replication.

Dataset Information

Macrophage-induced genes of Legionella pneumophila: protection from reactive intermediates and solute imbalance during intracellular growth.

Publications

Macrophage-induced genes of Legionella pneumophila: protection from reactive intermediates and solute imbalance during intracellular growth.

Similar Datasets

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