<named-content content-type="genus-species">Toxoplasma gondii</named-content> Parasitophorous Vacuole Membrane-Associated Dense Granule Proteins Regulate Maturation of the Cyst Wall

ABSTRACT After differentiation is triggered, the tachyzoite-stage Toxoplasma gondii parasitophorous vacuole membrane (PVM) has been hypothesized to transition into the cyst membrane that surrounds the cyst wall and encloses bradyzoites. Here, we tracked the localization of two PVM dense granule (GRA...

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Autores principales:	Rebekah B. Guevara, Barbara A. Fox, David J. Bzik
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	Toxoplasma gondii cysts chronic infection cyst wall cyst membrane parasitophorous vacuole membrane Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/3f45c4aa406b4e6eaf55482db85eaec7
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spelling	oai:doaj.org-article:3f45c4aa406b4e6eaf55482db85eaec72021-11-15T15:27:53Z<named-content content-type="genus-species">Toxoplasma gondii</named-content> Parasitophorous Vacuole Membrane-Associated Dense Granule Proteins Regulate Maturation of the Cyst Wall10.1128/mSphere.00851-192379-5042https://doaj.org/article/3f45c4aa406b4e6eaf55482db85eaec72020-02-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mSphere.00851-19https://doaj.org/toc/2379-5042ABSTRACT After differentiation is triggered, the tachyzoite-stage Toxoplasma gondii parasitophorous vacuole membrane (PVM) has been hypothesized to transition into the cyst membrane that surrounds the cyst wall and encloses bradyzoites. Here, we tracked the localization of two PVM dense granule (GRA) proteins (GRA5 and GRA7) after in vitro differentiation of the tachyzoite stage parasitophorous vacuole into the mature cyst. GRA5 and GRA7 were visible at the cyst periphery at 6 h and at all later times after differentiation, suggesting that the PVM remained intact as it transitioned into the cyst membrane. By day 3 postdifferentiation, GRA5 and GRA7 were visible in a continuous pattern at the cyst periphery. In mature 7- and 10-day-old cysts permeabilized with a saponin pulse, GRA5 and GRA7 were localized to the cyst membrane and the cyst wall regions. Cysts at different stages of cyst development exhibited differential susceptibility to saponin permeabilization, and, correspondingly, saponin selectively removed GRA5 from the cyst membrane and cyst wall region in 10-day-old cysts. GRA5 and GRA7 were localized at the cyst membrane and cyst wall region at all times after differentiation of the parasitophorous vacuole, which supports a previous model proposing that the PVM develops into the cyst membrane. In addition, evaluation of Δgra3, Δgra5, Δgra7, Δgra8, and Δgra14 mutants revealed that PVM-localized GRAs were crucial to support the normal rate of accumulation of cyst wall proteins at the cyst periphery. IMPORTANCE Toxoplasma gondii establishes chronic infection in humans by forming thick-walled cysts that persist in the brain. Once host immunity wanes, cysts reactivate to cause severe, and often lethal, toxoplasmic encephalitis. There is no available therapy to eliminate cysts or to prevent their reactivation. Furthermore, how the cyst membrane and cyst wall structures develop is poorly understood. Here, we visualized and tracked the localization of Toxoplasma parasitophorous vacuole membrane (PVM) dense granules (GRA) proteins during cyst development in vitro. PVM-localized GRA5 and GRA7 were found at the cyst membrane and cyst wall region throughout cyst development, suggesting that the PVM remains intact and develops into the cyst membrane. In addition, our results show that genetic deletion of PVM GRAs reduced the rate of accumulation of cyst wall cargo at the cyst periphery and suggest that PVM-localized GRAs mediate the development and maturation of the cyst wall and cyst membrane.Rebekah B. GuevaraBarbara A. FoxDavid J. BzikAmerican Society for MicrobiologyarticleToxoplasma gondiicystschronic infectioncyst wallcyst membraneparasitophorous vacuole membraneMicrobiologyQR1-502ENmSphere, Vol 5, Iss 1 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	Toxoplasma gondii cysts chronic infection cyst wall cyst membrane parasitophorous vacuole membrane Microbiology QR1-502
spellingShingle	Toxoplasma gondii cysts chronic infection cyst wall cyst membrane parasitophorous vacuole membrane Microbiology QR1-502 Rebekah B. Guevara Barbara A. Fox David J. Bzik <named-content content-type="genus-species">Toxoplasma gondii</named-content> Parasitophorous Vacuole Membrane-Associated Dense Granule Proteins Regulate Maturation of the Cyst Wall
description	ABSTRACT After differentiation is triggered, the tachyzoite-stage Toxoplasma gondii parasitophorous vacuole membrane (PVM) has been hypothesized to transition into the cyst membrane that surrounds the cyst wall and encloses bradyzoites. Here, we tracked the localization of two PVM dense granule (GRA) proteins (GRA5 and GRA7) after in vitro differentiation of the tachyzoite stage parasitophorous vacuole into the mature cyst. GRA5 and GRA7 were visible at the cyst periphery at 6 h and at all later times after differentiation, suggesting that the PVM remained intact as it transitioned into the cyst membrane. By day 3 postdifferentiation, GRA5 and GRA7 were visible in a continuous pattern at the cyst periphery. In mature 7- and 10-day-old cysts permeabilized with a saponin pulse, GRA5 and GRA7 were localized to the cyst membrane and the cyst wall regions. Cysts at different stages of cyst development exhibited differential susceptibility to saponin permeabilization, and, correspondingly, saponin selectively removed GRA5 from the cyst membrane and cyst wall region in 10-day-old cysts. GRA5 and GRA7 were localized at the cyst membrane and cyst wall region at all times after differentiation of the parasitophorous vacuole, which supports a previous model proposing that the PVM develops into the cyst membrane. In addition, evaluation of Δgra3, Δgra5, Δgra7, Δgra8, and Δgra14 mutants revealed that PVM-localized GRAs were crucial to support the normal rate of accumulation of cyst wall proteins at the cyst periphery. IMPORTANCE Toxoplasma gondii establishes chronic infection in humans by forming thick-walled cysts that persist in the brain. Once host immunity wanes, cysts reactivate to cause severe, and often lethal, toxoplasmic encephalitis. There is no available therapy to eliminate cysts or to prevent their reactivation. Furthermore, how the cyst membrane and cyst wall structures develop is poorly understood. Here, we visualized and tracked the localization of Toxoplasma parasitophorous vacuole membrane (PVM) dense granules (GRA) proteins during cyst development in vitro. PVM-localized GRA5 and GRA7 were found at the cyst membrane and cyst wall region throughout cyst development, suggesting that the PVM remains intact and develops into the cyst membrane. In addition, our results show that genetic deletion of PVM GRAs reduced the rate of accumulation of cyst wall cargo at the cyst periphery and suggest that PVM-localized GRAs mediate the development and maturation of the cyst wall and cyst membrane.
format	article
author	Rebekah B. Guevara Barbara A. Fox David J. Bzik
author_facet	Rebekah B. Guevara Barbara A. Fox David J. Bzik
author_sort	Rebekah B. Guevara
title	<named-content content-type="genus-species">Toxoplasma gondii</named-content> Parasitophorous Vacuole Membrane-Associated Dense Granule Proteins Regulate Maturation of the Cyst Wall
title_short	<named-content content-type="genus-species">Toxoplasma gondii</named-content> Parasitophorous Vacuole Membrane-Associated Dense Granule Proteins Regulate Maturation of the Cyst Wall
title_full	<named-content content-type="genus-species">Toxoplasma gondii</named-content> Parasitophorous Vacuole Membrane-Associated Dense Granule Proteins Regulate Maturation of the Cyst Wall
title_fullStr	<named-content content-type="genus-species">Toxoplasma gondii</named-content> Parasitophorous Vacuole Membrane-Associated Dense Granule Proteins Regulate Maturation of the Cyst Wall
title_full_unstemmed	<named-content content-type="genus-species">Toxoplasma gondii</named-content> Parasitophorous Vacuole Membrane-Associated Dense Granule Proteins Regulate Maturation of the Cyst Wall
title_sort	<named-content content-type="genus-species">toxoplasma gondii</named-content> parasitophorous vacuole membrane-associated dense granule proteins regulate maturation of the cyst wall
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/3f45c4aa406b4e6eaf55482db85eaec7
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<named-content content-type="genus-species">Toxoplasma gondii</named-content> Parasitophorous Vacuole Membrane-Associated Dense Granule Proteins Regulate Maturation of the Cyst Wall

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