Noncanonical Inhibition of mTORC1 by <named-content content-type="genus-species">Coxiella burnetii</named-content> Promotes Replication within a Phagolysosome-Like Vacuole

ABSTRACT The Q fever agent Coxiella burnetii is a Gram-negative bacterium that invades macrophages and replicates inside a specialized lysosomal vacuole. The pathogen employs a type 4B secretion system (T4BSS) to deliver effector proteins into the host cell that modify the Coxiella-containing vacuol...

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Autores principales:	Charles L. Larson, Kelsi M. Sandoz, Diane C. Cockrell, Robert A. Heinzen
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2019
Materias:	Coxiella Q fever autophagy coxiella-containing vacuole endolysosomal membranes lysosome Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/7824023c2cc14cbab101e8b0c9e102eb
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spelling	oai:doaj.org-article:7824023c2cc14cbab101e8b0c9e102eb2021-11-15T15:55:14ZNoncanonical Inhibition of mTORC1 by <named-content content-type="genus-species">Coxiella burnetii</named-content> Promotes Replication within a Phagolysosome-Like Vacuole10.1128/mBio.02816-182150-7511https://doaj.org/article/7824023c2cc14cbab101e8b0c9e102eb2019-02-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.02816-18https://doaj.org/toc/2150-7511ABSTRACT The Q fever agent Coxiella burnetii is a Gram-negative bacterium that invades macrophages and replicates inside a specialized lysosomal vacuole. The pathogen employs a type 4B secretion system (T4BSS) to deliver effector proteins into the host cell that modify the Coxiella-containing vacuole (CCV) into a replication-permissive niche. Mature CCVs are massive degradative organelles that acquire lysosomal proteins. Inhibition of mammalian (or mechanistic) target of rapamycin complex 1 (mTORC1) kinase by nutrient deprivation promotes autophagy and lysosome fusion, as well as activation of the transcription factors TFE3 and TFEB (TFE3/B), which upregulates expression of lysosomal genes. Here, we report that C. burnetii inhibits mTORC1 as evidenced by impaired localization of mTORC1 to endolysosomal membranes and decreased phosphorylation of elF4E-binding protein 1 (4E-BP1) and S6 kinase 1 in infected cells. Infected cells exhibit increased amounts of autophagy-related proteins protein 1A/1B-light chain 3 (LC3) and p62 as well as of activated TFE3. However, C. burnetii did not accelerate autophagy or block autophagic flux triggered by cell starvation. Activation of autophagy or transcription by TFE3/B increased CCV expansion without enhancing bacterial replication. By contrast, knockdown of tuberous sclerosis complex 1 (TSC1) or TSC2, which hyperactivates mTORC1, impaired CCV expansion and bacterial replication. Together, these data demonstrate that specific inhibition of mTORC1 by C. burnetii, but not amplified cell catabolism via autophagy, is required for optimal pathogen replication. These data reveal a complex interplay between lysosomal function and host cell metabolism that regulates C. burnetii intracellular growth. IMPORTANCE Coxiella burnetii is an intracellular pathogenic bacterium that replicates within a lysosomal vacuole. Biogenesis of the Coxiella-containing vacuole (CCV) requires effector proteins delivered into the host cell cytosol by the type 4B secretion system (T4BSS). Modifications to lysosomal physiology required for pathogen replication within the CCV are poorly understood. Mammalian (or mechanistic) target of rapamycin complex 1 (mTORC1) is a master kinase that regulates lysosome structure and function. Nutrient deprivation inhibits mTORC1, which promotes cell catabolism in the form of accelerated autophagy and increased lysosome biosynthesis. Here, we report that C. burnetii growth is enhanced by T4BSS-dependent inhibition of mTORC1 that does not activate autophagy. Canonical inhibition of mTORC1 by starvation or inhibitor treatment that induces autophagic flux does not benefit C. burnetii growth. Furthermore, hyperactivation of mTORC1 impairs bacterial replication. These findings indicate that C. burnetii inhibition of mTORC1 without accelerated autophagy promotes bacterial growth.Charles L. LarsonKelsi M. SandozDiane C. CockrellRobert A. HeinzenAmerican Society for MicrobiologyarticleCoxiellaQ feverautophagycoxiella-containing vacuoleendolysosomal membraneslysosomeMicrobiologyQR1-502ENmBio, Vol 10, Iss 1 (2019)
institution	DOAJ
collection	DOAJ
language	EN
topic	Coxiella Q fever autophagy coxiella-containing vacuole endolysosomal membranes lysosome Microbiology QR1-502
spellingShingle	Coxiella Q fever autophagy coxiella-containing vacuole endolysosomal membranes lysosome Microbiology QR1-502 Charles L. Larson Kelsi M. Sandoz Diane C. Cockrell Robert A. Heinzen Noncanonical Inhibition of mTORC1 by <named-content content-type="genus-species">Coxiella burnetii</named-content> Promotes Replication within a Phagolysosome-Like Vacuole
description	ABSTRACT The Q fever agent Coxiella burnetii is a Gram-negative bacterium that invades macrophages and replicates inside a specialized lysosomal vacuole. The pathogen employs a type 4B secretion system (T4BSS) to deliver effector proteins into the host cell that modify the Coxiella-containing vacuole (CCV) into a replication-permissive niche. Mature CCVs are massive degradative organelles that acquire lysosomal proteins. Inhibition of mammalian (or mechanistic) target of rapamycin complex 1 (mTORC1) kinase by nutrient deprivation promotes autophagy and lysosome fusion, as well as activation of the transcription factors TFE3 and TFEB (TFE3/B), which upregulates expression of lysosomal genes. Here, we report that C. burnetii inhibits mTORC1 as evidenced by impaired localization of mTORC1 to endolysosomal membranes and decreased phosphorylation of elF4E-binding protein 1 (4E-BP1) and S6 kinase 1 in infected cells. Infected cells exhibit increased amounts of autophagy-related proteins protein 1A/1B-light chain 3 (LC3) and p62 as well as of activated TFE3. However, C. burnetii did not accelerate autophagy or block autophagic flux triggered by cell starvation. Activation of autophagy or transcription by TFE3/B increased CCV expansion without enhancing bacterial replication. By contrast, knockdown of tuberous sclerosis complex 1 (TSC1) or TSC2, which hyperactivates mTORC1, impaired CCV expansion and bacterial replication. Together, these data demonstrate that specific inhibition of mTORC1 by C. burnetii, but not amplified cell catabolism via autophagy, is required for optimal pathogen replication. These data reveal a complex interplay between lysosomal function and host cell metabolism that regulates C. burnetii intracellular growth. IMPORTANCE Coxiella burnetii is an intracellular pathogenic bacterium that replicates within a lysosomal vacuole. Biogenesis of the Coxiella-containing vacuole (CCV) requires effector proteins delivered into the host cell cytosol by the type 4B secretion system (T4BSS). Modifications to lysosomal physiology required for pathogen replication within the CCV are poorly understood. Mammalian (or mechanistic) target of rapamycin complex 1 (mTORC1) is a master kinase that regulates lysosome structure and function. Nutrient deprivation inhibits mTORC1, which promotes cell catabolism in the form of accelerated autophagy and increased lysosome biosynthesis. Here, we report that C. burnetii growth is enhanced by T4BSS-dependent inhibition of mTORC1 that does not activate autophagy. Canonical inhibition of mTORC1 by starvation or inhibitor treatment that induces autophagic flux does not benefit C. burnetii growth. Furthermore, hyperactivation of mTORC1 impairs bacterial replication. These findings indicate that C. burnetii inhibition of mTORC1 without accelerated autophagy promotes bacterial growth.
format	article
author	Charles L. Larson Kelsi M. Sandoz Diane C. Cockrell Robert A. Heinzen
author_facet	Charles L. Larson Kelsi M. Sandoz Diane C. Cockrell Robert A. Heinzen
author_sort	Charles L. Larson
title	Noncanonical Inhibition of mTORC1 by <named-content content-type="genus-species">Coxiella burnetii</named-content> Promotes Replication within a Phagolysosome-Like Vacuole
title_short	Noncanonical Inhibition of mTORC1 by <named-content content-type="genus-species">Coxiella burnetii</named-content> Promotes Replication within a Phagolysosome-Like Vacuole
title_full	Noncanonical Inhibition of mTORC1 by <named-content content-type="genus-species">Coxiella burnetii</named-content> Promotes Replication within a Phagolysosome-Like Vacuole
title_fullStr	Noncanonical Inhibition of mTORC1 by <named-content content-type="genus-species">Coxiella burnetii</named-content> Promotes Replication within a Phagolysosome-Like Vacuole
title_full_unstemmed	Noncanonical Inhibition of mTORC1 by <named-content content-type="genus-species">Coxiella burnetii</named-content> Promotes Replication within a Phagolysosome-Like Vacuole
title_sort	noncanonical inhibition of mtorc1 by <named-content content-type="genus-species">coxiella burnetii</named-content> promotes replication within a phagolysosome-like vacuole
publisher	American Society for Microbiology
publishDate	2019
url	https://doaj.org/article/7824023c2cc14cbab101e8b0c9e102eb
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Noncanonical Inhibition of mTORC1 by <named-content content-type="genus-species">Coxiella burnetii</named-content> Promotes Replication within a Phagolysosome-Like Vacuole

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