Formate Promotes <italic toggle="yes">Shigella</italic> Intercellular Spread and Virulence Gene Expression

ABSTRACT The intracellular human pathogen Shigella flexneri invades the colon epithelium, replicates to high cell density within the host cell, and then spreads to adjacent epithelial cells. When S. flexneri gains access to the host cytosol, the bacteria metabolize host cytosolic carbon using glycol...

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Autores principales:	Benjamin J. Koestler, Carolyn R. Fisher, Shelley M. Payne
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2018
Materias:	Shigella formate metabolism virulence regulation Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/3d4af23aa2ad455fbd66535d4396725d
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spelling	oai:doaj.org-article:3d4af23aa2ad455fbd66535d4396725d2021-11-15T15:58:21ZFormate Promotes <italic toggle="yes">Shigella</italic> Intercellular Spread and Virulence Gene Expression10.1128/mBio.01777-182150-7511https://doaj.org/article/3d4af23aa2ad455fbd66535d4396725d2018-11-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01777-18https://doaj.org/toc/2150-7511ABSTRACT The intracellular human pathogen Shigella flexneri invades the colon epithelium, replicates to high cell density within the host cell, and then spreads to adjacent epithelial cells. When S. flexneri gains access to the host cytosol, the bacteria metabolize host cytosolic carbon using glycolysis and mixed acid fermentation, producing formate as a by-product. We show that S. flexneri infection results in the accumulation of formate within the host cell. Loss of pyruvate formate lyase (PFL; ΔpflB), which converts pyruvate to acetyl coenzyme A (CoA) and formate, eliminates S. flexneri formate production and reduces the ability of S. flexneri to form plaques in epithelial cell monolayers. This defect in PFL does not decrease the intracellular growth rate of S. flexneri; rather, it affects cell-to-cell spread. The S. flexneri ΔpflB mutant plaque defect is complemented by supplying exogenous formate; conversely, deletion of the S. flexneri formate dehydrogenase gene fdnG increases host cell formate accumulation and S. flexneri plaque size. Furthermore, exogenous formate increases plaque size of the wild-type (WT) S. flexneri strain and promotes S. flexneri cell-to-cell spread. We also demonstrate that formate increases the expression of S. flexneri virulence genes icsA and ipaJ. Intracellular S. flexneri icsA and ipaJ expression is dependent on the presence of formate, and ipaJ expression correlates with S. flexneri intracellular density during infection. Finally, consistent with elevated ipaJ, we show that formate alters S. flexneri-infected host interferon- and tumor necrosis factor (TNF)-stimulated gene expression. We propose that Shigella-derived formate is an intracellular signal that modulates virulence in response to bacterial metabolism. IMPORTANCE Shigella is an intracellular pathogen that invades the human host cell cytosol and exploits intracellular nutrients for growth, enabling the bacterium to create its own metabolic niche. For Shigella to effectively invade and replicate within the host cytoplasm, it must sense and adapt to changing environmental conditions; however, the mechanisms and signals sensed by S. flexneri are largely unknown. We have found that the secreted Shigella metabolism by-product formate regulates Shigella intracellular virulence gene expression and its ability to spread among epithelial cells. We propose that Shigella senses formate accumulation in the host cytosol as a way to determine intracellular Shigella density and regulate secreted virulence factors accordingly, enabling spatiotemporal regulation of effectors important for dampening the host immune response.Benjamin J. KoestlerCarolyn R. FisherShelley M. PayneAmerican Society for MicrobiologyarticleShigellaformatemetabolismvirulence regulationMicrobiologyQR1-502ENmBio, Vol 9, Iss 5 (2018)
institution	DOAJ
collection	DOAJ
language	EN
topic	Shigella formate metabolism virulence regulation Microbiology QR1-502
spellingShingle	Shigella formate metabolism virulence regulation Microbiology QR1-502 Benjamin J. Koestler Carolyn R. Fisher Shelley M. Payne Formate Promotes <italic toggle="yes">Shigella</italic> Intercellular Spread and Virulence Gene Expression
description	ABSTRACT The intracellular human pathogen Shigella flexneri invades the colon epithelium, replicates to high cell density within the host cell, and then spreads to adjacent epithelial cells. When S. flexneri gains access to the host cytosol, the bacteria metabolize host cytosolic carbon using glycolysis and mixed acid fermentation, producing formate as a by-product. We show that S. flexneri infection results in the accumulation of formate within the host cell. Loss of pyruvate formate lyase (PFL; ΔpflB), which converts pyruvate to acetyl coenzyme A (CoA) and formate, eliminates S. flexneri formate production and reduces the ability of S. flexneri to form plaques in epithelial cell monolayers. This defect in PFL does not decrease the intracellular growth rate of S. flexneri; rather, it affects cell-to-cell spread. The S. flexneri ΔpflB mutant plaque defect is complemented by supplying exogenous formate; conversely, deletion of the S. flexneri formate dehydrogenase gene fdnG increases host cell formate accumulation and S. flexneri plaque size. Furthermore, exogenous formate increases plaque size of the wild-type (WT) S. flexneri strain and promotes S. flexneri cell-to-cell spread. We also demonstrate that formate increases the expression of S. flexneri virulence genes icsA and ipaJ. Intracellular S. flexneri icsA and ipaJ expression is dependent on the presence of formate, and ipaJ expression correlates with S. flexneri intracellular density during infection. Finally, consistent with elevated ipaJ, we show that formate alters S. flexneri-infected host interferon- and tumor necrosis factor (TNF)-stimulated gene expression. We propose that Shigella-derived formate is an intracellular signal that modulates virulence in response to bacterial metabolism. IMPORTANCE Shigella is an intracellular pathogen that invades the human host cell cytosol and exploits intracellular nutrients for growth, enabling the bacterium to create its own metabolic niche. For Shigella to effectively invade and replicate within the host cytoplasm, it must sense and adapt to changing environmental conditions; however, the mechanisms and signals sensed by S. flexneri are largely unknown. We have found that the secreted Shigella metabolism by-product formate regulates Shigella intracellular virulence gene expression and its ability to spread among epithelial cells. We propose that Shigella senses formate accumulation in the host cytosol as a way to determine intracellular Shigella density and regulate secreted virulence factors accordingly, enabling spatiotemporal regulation of effectors important for dampening the host immune response.
format	article
author	Benjamin J. Koestler Carolyn R. Fisher Shelley M. Payne
author_facet	Benjamin J. Koestler Carolyn R. Fisher Shelley M. Payne
author_sort	Benjamin J. Koestler
title	Formate Promotes <italic toggle="yes">Shigella</italic> Intercellular Spread and Virulence Gene Expression
title_short	Formate Promotes <italic toggle="yes">Shigella</italic> Intercellular Spread and Virulence Gene Expression
title_full	Formate Promotes <italic toggle="yes">Shigella</italic> Intercellular Spread and Virulence Gene Expression
title_fullStr	Formate Promotes <italic toggle="yes">Shigella</italic> Intercellular Spread and Virulence Gene Expression
title_full_unstemmed	Formate Promotes <italic toggle="yes">Shigella</italic> Intercellular Spread and Virulence Gene Expression
title_sort	formate promotes <italic toggle="yes">shigella</italic> intercellular spread and virulence gene expression
publisher	American Society for Microbiology
publishDate	2018
url	https://doaj.org/article/3d4af23aa2ad455fbd66535d4396725d
work_keys_str_mv	AT benjaminjkoestler formatepromotesitalictoggleyesshigellaitalicintercellularspreadandvirulencegeneexpression AT carolynrfisher formatepromotesitalictoggleyesshigellaitalicintercellularspreadandvirulencegeneexpression AT shelleympayne formatepromotesitalictoggleyesshigellaitalicintercellularspreadandvirulencegeneexpression
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Formate Promotes <italic toggle="yes">Shigella</italic> Intercellular Spread and Virulence Gene Expression

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