Dataset Information

Characterization of Chlamydial Rho and the Role of Rho-Mediated Transcriptional Polarity during Interferon Gamma-Mediated Tryptophan Limitation.

ABSTRACT: As an obligate intracellular, developmentally regulated bacterium, Chlamydia is sensitive to amino acid fluctuations within its host cell. When human epithelial cells are treated with the cytokine interferon gamma (IFN-?), the tryptophan (Trp)-degrading enzyme, indoleamine-2,3-dioxygenase, is induced. Chlamydiae within such cells are starved for Trp and enter a state of so-called persistence. Chlamydia lacks the stringent response used by many eubacteria to respond to this stress. Unusually, chlamydial transcription is globally elevated during Trp starvation with transcripts for Trp codon-containing genes disproportionately increased. Yet, the presence of Trp codons destabilized 3' ends of transcripts in operons or large genes. We initially hypothesized that ribosome stalling on Trp codons rendered the 3' ends sensitive to RNase activity. The half-life of chlamydial transcripts containing different numbers of Trp codons was thus measured in untreated and IFN-?-treated infected cells to determine whether Trp codons influenced the stability of transcripts. However, no effect of Trp codon content was detected. Therefore, we investigated whether Rho-dependent transcription termination could play a role in mediating transcript instability. Rho is expressed as a midcycle gene product, interacts with itself as predicted, and is present in all chlamydial species. Inhibition of Rho via the Rho-specific antibiotic, bicyclomycin, and overexpression of Rho are detrimental to chlamydiae. Finally, when we measured transcript abundance 3' to Trp codons in the presence of bicyclomycin, we observed that transcript abundance increased. These data are the first to demonstrate the importance of Rho in Chlamydia and the role of Rho-dependent transcription polarity during persistence.

SUBMITTER: Ouellette SP

PROVIDER: S-EPMC6013675 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Characterization of Chlamydial Rho and the Role of Rho-Mediated Transcriptional Polarity during Interferon Gamma-Mediated Tryptophan Limitation.

Ouellette Scot P SP Messerli Parker R PR Wood Nicholas A NA Hajovsky Heather H

Infection and immunity 20180621 7

As an obligate intracellular, developmentally regulated bacterium, <i>Chlamydia</i> is sensitive to amino acid fluctuations within its host cell. When human epithelial cells are treated with the cytokine interferon gamma (IFN-γ), the tryptophan (Trp)-degrading enzyme, indoleamine-2,3-dioxygenase, is induced. Chlamydiae within such cells are starved for Trp and enter a state of so-called persistence. <i>Chlamydia</i> lacks the stringent response used by many eubacteria to respond to this stress. ...[more]

PMID: 29712731

Similar Datasets

Project description:The human immune response that controls Plasmodium infection in the liver and blood stages of the parasite life cycle is composed by both pro- and anti-inflammatory programs. Pro-inflammatory responses primarily mediated by IFN-γ controls the infection, but also induce tolerogenic mechanisms to limit host damage, including the tryptophan (TRP) catabolism pathway mediated by the enzyme Indoleamine 2,3-Dioxygenase (IDO1), an enzyme that catalyzes the degradation of TRP to kynurenines (KYN). Here we assessed total serum kynurenines and cytokine dynamics in a cohort of natural Plasmodium vivax human infection and compared them to those of endemic healthy controls and other febrile diseases. In acute malaria, the absolute free kynurenine (KYN) serum levels and the KYN to TRP (KYN/TRP) ratio were significantly elevated in patients compared to healthy controls. Individuals with a diagnosis of a first malaria episode had higher serum KYN levels than individuals with a previous malaria episode. We observed an inverse relationship between the serum levels of IFN-γ and IL-10 in patients with a first malaria episode compared to those of subjects with previous history of malaria. Kynurenine elevation was positively correlated with serum IFN-γ levels in acute infection, whereas, it was negatively correlated with parasite load and P. vivax LDH levels. Overall, the differences observed between infected individuals depended on the number of Plasmodium infections. The decrease in the KYN/TRP ratio in malaria-experienced subjects coincided with the onset of anti-P. vivax IgG. These results suggest that P. vivax infection induces a strong anti-inflammatory program in individuals with first time malaria, which fades with ensuing protective immunity after subsequent episodes. Understanding the tolerance mechanisms involved in the initial exposure would help in defining the balance between protective and pathogenic immune responses necessary to control infection and to improve vaccination strategies.

Project description:BackgroundEndothelial cells depend on glycolysis for much of their energy production. Impaired endothelial glycolysis has been associated with various vascular pathobiologies, including impaired angiogenesis and atherogenesis. IFN-γ (interferon-γ)-producing CD4+ and CD8+ T lymphocytes have been identified as the predominant pathological cell subsets in human atherosclerotic plaques. Although the immunologic consequences of these cells have been extensively evaluated, their IFN-γ-mediated metabolic effects on endothelial cells remain unknown. The purpose of this study was to determine the metabolic consequences of the T-lymphocyte cytokine, IFN-γ, on human coronary artery endothelial cells.MethodsThe metabolic effects of IFN-γ on primary human coronary artery endothelial cells were assessed by unbiased transcriptomic and metabolomic analyses combined with real-time extracellular flux analyses and molecular mechanistic studies. Cellular phenotypic correlations were made by measuring altered endothelial intracellular cGMP content, wound-healing capacity, and adhesion molecule expression.ResultsIFN-γ exposure inhibited basal glycolysis of quiescent primary human coronary artery endothelial cells by 20% through the global transcriptional suppression of glycolytic enzymes resulting from decreased basal HIF1α (hypoxia-inducible factor 1α) nuclear availability in normoxia. The decrease in HIF1α activity was a consequence of IFN-γ-induced tryptophan catabolism resulting in ARNT (aryl hydrocarbon receptor nuclear translocator)/HIF1β sequestration by the kynurenine-activated AHR (aryl hydrocarbon receptor). In addition, IFN-γ resulted in a 23% depletion of intracellular nicotinamide adenine dinucleotide in human coronary artery endothelial cells. This altered glucose metabolism was met with concomitant activation of fatty acid oxidation, which augmented its contribution to intracellular ATP balance by >20%. These metabolic derangements were associated with adverse endothelial phenotypic changes, including decreased basal intracellular cGMP, impaired endothelial migration, and a switch to a proinflammatory state.ConclusionsIFN-γ impairs endothelial glucose metabolism by altered tryptophan catabolism destabilizing HIF1, depletes nicotinamide adenine dinucleotide, and results in a metabolic shift toward increased fatty acid oxidation. This work suggests a novel mechanistic basis for pathological T lymphocyte-endothelial interactions in atherosclerosis mediated by IFN-γ, linking endothelial glucose, tryptophan, and fatty acid metabolism with the nicotinamide adenine dinucleotide balance and ATP generation and their adverse endothelial functional consequences.

Dataset Information

Characterization of Chlamydial Rho and the Role of Rho-Mediated Transcriptional Polarity during Interferon Gamma-Mediated Tryptophan Limitation.

Publications

Characterization of Chlamydial Rho and the Role of Rho-Mediated Transcriptional Polarity during Interferon Gamma-Mediated Tryptophan Limitation.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets