Escape of Actively Secreting <named-content content-type="genus-species">Shigella flexneri</named-content> from ATG8/LC3-Positive Vacuoles Formed during Cell-To-Cell Spread Is Facilitated by IcsB and VirA

ABSTRACT The enteropathogenic bacterium Shigella flexneri uses a type 3 secretion apparatus (T3SA) to transfer proteins dubbed translocators and effectors inside host cells, inducing bacterial uptake and subsequent lysis of the entry vacuole. Once in the cytoplasm, the outer membrane protein IcsA in...

Descripción completa

Guardado en:

Detalles Bibliográficos
Autores principales:	François-Xavier Campbell-Valois, Martin Sachse, Philippe J. Sansonetti, Claude Parsot
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2015
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/e959c8a360154136b755b7e35c93173b
Etiquetas:	Agregar Etiqueta Sin Etiquetas, Sea el primero en etiquetar este registro!

id	oai:doaj.org-article:e959c8a360154136b755b7e35c93173b
record_format	dspace
spelling	oai:doaj.org-article:e959c8a360154136b755b7e35c93173b2021-11-15T15:49:02ZEscape of Actively Secreting <named-content content-type="genus-species">Shigella flexneri</named-content> from ATG8/LC3-Positive Vacuoles Formed during Cell-To-Cell Spread Is Facilitated by IcsB and VirA10.1128/mBio.02567-142150-7511https://doaj.org/article/e959c8a360154136b755b7e35c93173b2015-07-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.02567-14https://doaj.org/toc/2150-7511ABSTRACT The enteropathogenic bacterium Shigella flexneri uses a type 3 secretion apparatus (T3SA) to transfer proteins dubbed translocators and effectors inside host cells, inducing bacterial uptake and subsequent lysis of the entry vacuole. Once in the cytoplasm, the outer membrane protein IcsA induces actin polymerization, enabling cytoplasmic movement and cell-to-cell spread of bacteria. During this infectious process, S. flexneri is targeted by ATG8/LC3. The effector IcsB was proposed to inhibit LC3 recruitment by masking a region of IcsA recognized by the autophagy pathway component ATG5. The effector VirA, a GTPase-activating protein (GAP) for Rab1, was also shown to prevent LC3 recruitment. However, the context of LC3 recruitment around S. flexneri is not fully understood. Here, we show that LC3 is recruited specifically around secreting bacteria that are still present in vacuoles formed during entry and cell-to-cell spread. While LC3 recruitment occurs around a small proportion of intracellular wild-type bacteria, the icsB, virA, and icsB virA mutants display incremental defaults in escape from LC3-positive vacuoles formed during cell-to-cell spread. Our results indicate that IcsB and VirA act synergistically to allow bacteria to escape from LC3-positive vacuoles by acting at or in the immediate vicinity of the vacuole membrane(s). We also demonstrate that LC3 is recruited around bacteria still present in the single-membrane entry vacuole, in a manner akin to that seen with LC3-associated phagocytosis. Our results indicate that LC3 recruitment occurs around bacteria still, or already, in membrane compartments formed during entry and cell-to-cell spread, and not around bacteria free in the cytoplasm. IMPORTANCE The targeting of S. flexneri by LC3 is a classic example of the targeting of foreign cytoplasmic particles by autophagy (so-called “xenoautophagy”). It is often assumed that LC3 is recruited around bacteria present in the cytoplasm through the formation of canonical double-membrane autophagosomes. Our results indicate that LC3 is recruited around the entry vacuole composed of a single membrane as in the case of LC3-associated phagocytosis. Effectors IcsB and VirA had been implicated in the blocking of LC3 recruitment, but it was not known if they acted on the same or distinct LC3-recruiting pathways. Our results indicate that LC3 is recruited exclusively around bacteria present in vacuoles formed during entry and cell-to-cell spread and that both IcsB and VirA intervene at the latter stage to facilitate bacterial escape. Our report reconciles several findings and may have broad implications for our understanding of the specific targeting of bacterial pathogens by LC3.François-Xavier Campbell-ValoisMartin SachsePhilippe J. SansonettiClaude ParsotAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 6, Iss 3 (2015)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 François-Xavier Campbell-Valois Martin Sachse Philippe J. Sansonetti Claude Parsot Escape of Actively Secreting <named-content content-type="genus-species">Shigella flexneri</named-content> from ATG8/LC3-Positive Vacuoles Formed during Cell-To-Cell Spread Is Facilitated by IcsB and VirA
description	ABSTRACT The enteropathogenic bacterium Shigella flexneri uses a type 3 secretion apparatus (T3SA) to transfer proteins dubbed translocators and effectors inside host cells, inducing bacterial uptake and subsequent lysis of the entry vacuole. Once in the cytoplasm, the outer membrane protein IcsA induces actin polymerization, enabling cytoplasmic movement and cell-to-cell spread of bacteria. During this infectious process, S. flexneri is targeted by ATG8/LC3. The effector IcsB was proposed to inhibit LC3 recruitment by masking a region of IcsA recognized by the autophagy pathway component ATG5. The effector VirA, a GTPase-activating protein (GAP) for Rab1, was also shown to prevent LC3 recruitment. However, the context of LC3 recruitment around S. flexneri is not fully understood. Here, we show that LC3 is recruited specifically around secreting bacteria that are still present in vacuoles formed during entry and cell-to-cell spread. While LC3 recruitment occurs around a small proportion of intracellular wild-type bacteria, the icsB, virA, and icsB virA mutants display incremental defaults in escape from LC3-positive vacuoles formed during cell-to-cell spread. Our results indicate that IcsB and VirA act synergistically to allow bacteria to escape from LC3-positive vacuoles by acting at or in the immediate vicinity of the vacuole membrane(s). We also demonstrate that LC3 is recruited around bacteria still present in the single-membrane entry vacuole, in a manner akin to that seen with LC3-associated phagocytosis. Our results indicate that LC3 recruitment occurs around bacteria still, or already, in membrane compartments formed during entry and cell-to-cell spread, and not around bacteria free in the cytoplasm. IMPORTANCE The targeting of S. flexneri by LC3 is a classic example of the targeting of foreign cytoplasmic particles by autophagy (so-called “xenoautophagy”). It is often assumed that LC3 is recruited around bacteria present in the cytoplasm through the formation of canonical double-membrane autophagosomes. Our results indicate that LC3 is recruited around the entry vacuole composed of a single membrane as in the case of LC3-associated phagocytosis. Effectors IcsB and VirA had been implicated in the blocking of LC3 recruitment, but it was not known if they acted on the same or distinct LC3-recruiting pathways. Our results indicate that LC3 is recruited exclusively around bacteria present in vacuoles formed during entry and cell-to-cell spread and that both IcsB and VirA intervene at the latter stage to facilitate bacterial escape. Our report reconciles several findings and may have broad implications for our understanding of the specific targeting of bacterial pathogens by LC3.
format	article
author	François-Xavier Campbell-Valois Martin Sachse Philippe J. Sansonetti Claude Parsot
author_facet	François-Xavier Campbell-Valois Martin Sachse Philippe J. Sansonetti Claude Parsot
author_sort	François-Xavier Campbell-Valois
title	Escape of Actively Secreting <named-content content-type="genus-species">Shigella flexneri</named-content> from ATG8/LC3-Positive Vacuoles Formed during Cell-To-Cell Spread Is Facilitated by IcsB and VirA
title_short	Escape of Actively Secreting <named-content content-type="genus-species">Shigella flexneri</named-content> from ATG8/LC3-Positive Vacuoles Formed during Cell-To-Cell Spread Is Facilitated by IcsB and VirA
title_full	Escape of Actively Secreting <named-content content-type="genus-species">Shigella flexneri</named-content> from ATG8/LC3-Positive Vacuoles Formed during Cell-To-Cell Spread Is Facilitated by IcsB and VirA
title_fullStr	Escape of Actively Secreting <named-content content-type="genus-species">Shigella flexneri</named-content> from ATG8/LC3-Positive Vacuoles Formed during Cell-To-Cell Spread Is Facilitated by IcsB and VirA
title_full_unstemmed	Escape of Actively Secreting <named-content content-type="genus-species">Shigella flexneri</named-content> from ATG8/LC3-Positive Vacuoles Formed during Cell-To-Cell Spread Is Facilitated by IcsB and VirA
title_sort	escape of actively secreting <named-content content-type="genus-species">shigella flexneri</named-content> from atg8/lc3-positive vacuoles formed during cell-to-cell spread is facilitated by icsb and vira
publisher	American Society for Microbiology
publishDate	2015
url	https://doaj.org/article/e959c8a360154136b755b7e35c93173b
work_keys_str_mv	AT francoisxaviercampbellvalois escapeofactivelysecretingnamedcontentcontenttypegenusspeciesshigellaflexnerinamedcontentfromatg8lc3positivevacuolesformedduringcelltocellspreadisfacilitatedbyicsbandvira AT martinsachse escapeofactivelysecretingnamedcontentcontenttypegenusspeciesshigellaflexnerinamedcontentfromatg8lc3positivevacuolesformedduringcelltocellspreadisfacilitatedbyicsbandvira AT philippejsansonetti escapeofactivelysecretingnamedcontentcontenttypegenusspeciesshigellaflexnerinamedcontentfromatg8lc3positivevacuolesformedduringcelltocellspreadisfacilitatedbyicsbandvira AT claudeparsot escapeofactivelysecretingnamedcontentcontenttypegenusspeciesshigellaflexnerinamedcontentfromatg8lc3positivevacuolesformedduringcelltocellspreadisfacilitatedbyicsbandvira
_version_	1718427494618497024

Escape of Actively Secreting <named-content content-type="genus-species">Shigella flexneri</named-content> from ATG8/LC3-Positive Vacuoles Formed during Cell-To-Cell Spread Is Facilitated by IcsB and VirA

Ejemplares similares