A Noncanonical Autophagy Pathway Restricts <named-content content-type="genus-species">Toxoplasma gondii</named-content> Growth in a Strain-Specific Manner in IFN-γ-Activated Human Cells

ABSTRACT A core set of autophagy proteins is required for gamma interferon (IFN-γ)-mediated clearance of Toxoplasma gondii in the mouse because of their control of several downstream effectors, including immunity-related GTPases (IRGs) and guanylate-binding proteins (GBPs). However, these effectors...

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Autores principales:	Elizabeth M. Selleck, Robert C. Orchard, Kara G. Lassen, Wandy L. Beatty, Ramnik J. Xavier, Beth Levine, Herbert W. Virgin, L. David Sibley
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2015
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/28b393fbe97e4760a7ecc6c932e146bd
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spelling	oai:doaj.org-article:28b393fbe97e4760a7ecc6c932e146bd2021-11-15T15:41:31ZA Noncanonical Autophagy Pathway Restricts <named-content content-type="genus-species">Toxoplasma gondii</named-content> Growth in a Strain-Specific Manner in IFN-γ-Activated Human Cells10.1128/mBio.01157-152150-7511https://doaj.org/article/28b393fbe97e4760a7ecc6c932e146bd2015-10-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01157-15https://doaj.org/toc/2150-7511ABSTRACT A core set of autophagy proteins is required for gamma interferon (IFN-γ)-mediated clearance of Toxoplasma gondii in the mouse because of their control of several downstream effectors, including immunity-related GTPases (IRGs) and guanylate-binding proteins (GBPs). However, these effectors are absent (i.e., IRGs) from or nonessential (i.e., GBPs) in IFN-γ-activated human cells, raising the question of how these cells control parasite replication. Here, we define a novel role for ubiquitination and recruitment of autophagy adaptors in the strain-specific control of T. gondii replication in IFN-γ-activated human cells. Vacuoles containing susceptible strains of T. gondii became ubiquitinated, recruited the adaptors p62 and NDP52, and were decorated with LC3. Parasites within LC3-positive vacuoles became enclosed in multiple layers of host membranes, resulting in stunting of parasite replication. However, LC3-positive T. gondii-containing vacuoles did not fuse with endosomes and lysosomes, indicating that this process is fundamentally different from xenophagy, a form of autophagy involved in the control of intracellular bacterial pathogens. Genetic knockout of ATG16L or ATG7 reverted the membrane encapsulation and restored parasite replication, indicating that core autophagy proteins involved in LC3 conjugation are important in the control of parasite growth. Despite a role for the core autophagy machinery in this process, upstream activation through Beclin 1 was not sufficient to enhance the ubiquitination of T. gondii-containing vacuoles, suggesting a lack of reliance on canonical autophagy. These findings demonstrate a new mechanism for IFN-γ-dependent control of T. gondii in human cells that depends on ubiquitination and core autophagy proteins that mediate membrane engulfment and restricted growth. IMPORTANCE Autophagy is a process of cellular remodeling that allows the cell to recycle senescent organelles and recapture nutrients. During innate immune responses in the mouse, autophagy is recruited to help target intracellular pathogens and thus eliminate them. However, the antimicrobial mediators that depend on autophagy in the mouse are not conserved in humans, raising the issue of how human cells control intracellular pathogens. Our study defines a new pathway for the control of the ubiquitous intracellular parasite T. gondii in human cells activated by IFN-γ. Recruitment of autophagy adaptors resulted in engulfment of the parasite in multiple membranes and growth impairment. Although susceptible type 2 and 3 stains of T. gondii were captured by this autophagy-dependent pathway, type 1 strains were able to avoid entrapment.Elizabeth M. SelleckRobert C. OrchardKara G. LassenWandy L. BeattyRamnik J. XavierBeth LevineHerbert W. VirginL. David SibleyAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 6, Iss 5 (2015)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Elizabeth M. Selleck Robert C. Orchard Kara G. Lassen Wandy L. Beatty Ramnik J. Xavier Beth Levine Herbert W. Virgin L. David Sibley A Noncanonical Autophagy Pathway Restricts <named-content content-type="genus-species">Toxoplasma gondii</named-content> Growth in a Strain-Specific Manner in IFN-γ-Activated Human Cells
description	ABSTRACT A core set of autophagy proteins is required for gamma interferon (IFN-γ)-mediated clearance of Toxoplasma gondii in the mouse because of their control of several downstream effectors, including immunity-related GTPases (IRGs) and guanylate-binding proteins (GBPs). However, these effectors are absent (i.e., IRGs) from or nonessential (i.e., GBPs) in IFN-γ-activated human cells, raising the question of how these cells control parasite replication. Here, we define a novel role for ubiquitination and recruitment of autophagy adaptors in the strain-specific control of T. gondii replication in IFN-γ-activated human cells. Vacuoles containing susceptible strains of T. gondii became ubiquitinated, recruited the adaptors p62 and NDP52, and were decorated with LC3. Parasites within LC3-positive vacuoles became enclosed in multiple layers of host membranes, resulting in stunting of parasite replication. However, LC3-positive T. gondii-containing vacuoles did not fuse with endosomes and lysosomes, indicating that this process is fundamentally different from xenophagy, a form of autophagy involved in the control of intracellular bacterial pathogens. Genetic knockout of ATG16L or ATG7 reverted the membrane encapsulation and restored parasite replication, indicating that core autophagy proteins involved in LC3 conjugation are important in the control of parasite growth. Despite a role for the core autophagy machinery in this process, upstream activation through Beclin 1 was not sufficient to enhance the ubiquitination of T. gondii-containing vacuoles, suggesting a lack of reliance on canonical autophagy. These findings demonstrate a new mechanism for IFN-γ-dependent control of T. gondii in human cells that depends on ubiquitination and core autophagy proteins that mediate membrane engulfment and restricted growth. IMPORTANCE Autophagy is a process of cellular remodeling that allows the cell to recycle senescent organelles and recapture nutrients. During innate immune responses in the mouse, autophagy is recruited to help target intracellular pathogens and thus eliminate them. However, the antimicrobial mediators that depend on autophagy in the mouse are not conserved in humans, raising the issue of how human cells control intracellular pathogens. Our study defines a new pathway for the control of the ubiquitous intracellular parasite T. gondii in human cells activated by IFN-γ. Recruitment of autophagy adaptors resulted in engulfment of the parasite in multiple membranes and growth impairment. Although susceptible type 2 and 3 stains of T. gondii were captured by this autophagy-dependent pathway, type 1 strains were able to avoid entrapment.
format	article
author	Elizabeth M. Selleck Robert C. Orchard Kara G. Lassen Wandy L. Beatty Ramnik J. Xavier Beth Levine Herbert W. Virgin L. David Sibley
author_facet	Elizabeth M. Selleck Robert C. Orchard Kara G. Lassen Wandy L. Beatty Ramnik J. Xavier Beth Levine Herbert W. Virgin L. David Sibley
author_sort	Elizabeth M. Selleck
title	A Noncanonical Autophagy Pathway Restricts <named-content content-type="genus-species">Toxoplasma gondii</named-content> Growth in a Strain-Specific Manner in IFN-γ-Activated Human Cells
title_short	A Noncanonical Autophagy Pathway Restricts <named-content content-type="genus-species">Toxoplasma gondii</named-content> Growth in a Strain-Specific Manner in IFN-γ-Activated Human Cells
title_full	A Noncanonical Autophagy Pathway Restricts <named-content content-type="genus-species">Toxoplasma gondii</named-content> Growth in a Strain-Specific Manner in IFN-γ-Activated Human Cells
title_fullStr	A Noncanonical Autophagy Pathway Restricts <named-content content-type="genus-species">Toxoplasma gondii</named-content> Growth in a Strain-Specific Manner in IFN-γ-Activated Human Cells
title_full_unstemmed	A Noncanonical Autophagy Pathway Restricts <named-content content-type="genus-species">Toxoplasma gondii</named-content> Growth in a Strain-Specific Manner in IFN-γ-Activated Human Cells
title_sort	noncanonical autophagy pathway restricts <named-content content-type="genus-species">toxoplasma gondii</named-content> growth in a strain-specific manner in ifn-γ-activated human cells
publisher	American Society for Microbiology
publishDate	2015
url	https://doaj.org/article/28b393fbe97e4760a7ecc6c932e146bd
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A Noncanonical Autophagy Pathway Restricts <named-content content-type="genus-species">Toxoplasma gondii</named-content> Growth in a Strain-Specific Manner in IFN-γ-Activated Human Cells

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