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Research Support, Non-U.S. Gov't
- Inhibition of eukaryotic translation by tetratricopeptide-repeat proteins of Orientia tsutsugamushi
- Sunyoung Bang , Chan-Ki Min , Na-Young Ha , Myung-Sik Choi , Ik-Sang Kim , Yeon-Sook Kim , Nam-Hyuk Cho
- J. Microbiol. 2016;54(2):136-144. Published online February 2, 2016
- DOI: https://doi.org/10.1007/s12275-016-5599-5
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- 8 Citations
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Abstract
- Orientia tsutsugamushi, an obligate intracellular bacterium, is the causative agent of scrub typhus. The genome of Orientia tsutsugamushi has revealed multiple ORFs encoding tetratricopeptide- repeat (TPR) proteins. The TPR protein family has been shown to be involved in a diverse spectrum of cellular functions such as cell cycle control, transcription, protein transport, and protein folding, especially in eukaryotic cells. However, little is known about the function of the TPR proteins in O. tsutsugamushi. To investigate the potential role of TPR proteins in host-pathogen interaction, two oriential TPR proteins were expressed in E. coli and applied for GSTpull down assay. DDX3, a DEAD-box containing RNA helicase, was identified as a specific eukaryotic target of the TPR proteins. Since the RNA helicase is involved in multiple RNAmodifying processes such as initiation of translation reaction, we performed in vitro translation assay in the presence of GST-TPR fusion proteins by using rabbit reticulocyte lysate system. The TPR proteins inhibited in vitro translation of a reporter luciferase in a dose dependent manner whereas the GST control proteins did not. These results suggested TPR proteins of O. tsutsugamushi might be involved in the modulation of eukarytotic translation through the interaction with DDX3 RNA helicase after secretion into host cytoplasm.
- Alterations in the Activities of Antioxidant Enzymes of Human Dermal Microvascular Endothelial Cells Infected with Orientia tsutsugamushi
- Young-Sang Koh
- J. Microbiol. 2001;39(2):142-145.
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Abstract
- Changes in the activities of several antioxidant enzymes in transformed human dermal microvascular endothelial cells (HMEC-1) by infection with the obligate intracellular bacterium Orientia tsutsugamushi, the causative agent of scrub typhus, were investigated. The activities of glucose-6-phosphate dehydrogenase, catalase, and glutathione peroxidase were significantly decreased in HMEC-1 cells infected with O. tsutsugamushi. However, the level of superoxide dismutase increased slightly. Furthermore, increased levels of intracellular peroxide was observed in HMEC-1 during infection. These results support the hypothesis that cells infected by this intracellular bacterium experience oxidant-mediated injury that may eventually contribute to cell death.
- Expression of Chemokine and Tumor Necrosis Factor Alpha Genes in Murine Peritoneal Macrophages Infected with Orientia tsutsugamushi
- Young-Sang Koh
- J. Microbiol. 2001;39(3):186-194.
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Abstract
- Scrub typhus, caused by Orientia tsutsugamushi infection, is clinically and histopathologically characterized by local as well as systemic inflammatory reactions, indicating that orientiae induce mechanisms that amplify the inflammatory response. To reveal underlying mechanisms of chemoattraction and activation of responding leukocytes, expression of chemokine and tumor necrosis factor alpha (TNF-[alpha]) genes in murine peritoneal macrophages after infection with the obligate intracellular bacterium O. tsutsugamushi was investigated. The genes that were upregulated included macrophage inflammatory proteins 1[alpha]/[beta] (MIP-1[alpha]/[beta]), MIP-2, monocyte chemoattractant protein 1 (MCP-1), RANTES (regulated upon activation, normal T-cell expressed and secreted), gamma-interferon-inducible protein 10 (IP-10), and TNF-[alpha]. Peak expression of these chemokines and TNF-[alpha] was observed between 1 and 3 h after infection. These responses returned to or approached baseline preinfection levels 6 h after challenge. Semiquantitative reverse transcription (RT)-PCR analysis revealed dramatic increases during infection in the steady-state levels of mRNA coding for the inhibitory subunit of NF-[kappa]B (I[kappa]B[alpha]), whose transcription is enhanced by binding of NF-[kappa]B within the I[kappa]B[alpha] promoter region. Thus, O. tsutsugamushi appears to be a strong inducer of chemokines and TNF-[alpha] which may significantly contribute to inflammation and tissue damage observed in scrub typhus by attracting and activating phagocytic leukocytes.
- Molecular Cloning of the Superoxide Dismutase Gene from Orientia tsutsugamushi, the Causative Agent of Scrub Typhus
- Ji-Hyun Yun , Young-Sang Koh , Se-Jae Kim
- J. Microbiol. 2002;40(2):151-155.
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Abstract
- A superoxide dismutase (SOD) gene from the obligate intracellular bacterium Orientia tsutsugamushi has been cloned by using the polymerase chain reaction with degenerate oligonucleotide primers corresponding to conserved regions of known SODs. Nucleotide sequencing revealed that the predicted amino acid sequence was significantly more homologous to known iron-containing SODs (FeSOD) than to manganese-containing SODs (MnSOD). Conserved regions in bacterial FeSOD could also be seen. Isolation of the oriential SOD gene may provide an opportunity to examine its role in the intracellular survival of this bacterium.
- Chemokine Gene Expression in Mice during Orientia tsutsugamushi Infection
- Young-Sang Koh
- J. Microbiol. 2003;41(3):266-270.
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Abstract
- Orientia tsutsugamushi, an obligate intracellular bacterium, is the causative agent of scrub typhus which is histopathologically characterized by inflammatory manifestations. To understand the pathogenesis of scrub typhus, chemokine gene expression in mice after infection with O. tsutsugamushi was investigated. The mRNAs that were upregulated included macrophage inflammatory proteins 1[alpha]/[beta] (MIP-1[alpha]/[beta]), MIP-2, monocyte chemoattractant protein 1, RANTES (regulated upon activation, normal T-cell expressed and secreted), and gamma-interferon-inducible protein 10. Peak expression of these chemokines was observed six days after infection. These responses returned to or approached baseline preinfection levels by eight days after infection. Chemokine profiles in infected mice were well correlated with the kinetics of inflammatory cell infiltration. Thus, O. tsutsugamushi appears to be a strong inducer of chemokines which may significantly contribute to the inflammation observed in scrub typhus by attracting and activating phagocytic leukocytes.
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