<italic toggle="yes">Toxoplasma</italic> Actin Is Required for Efficient Host Cell Invasion

ABSTRACT Apicomplexan parasites actively invade host cells using a mechanism predicted to be powered by a parasite actin-dependent myosin motor. In the model apicomplexan Toxoplasma gondii, inducible knockout of the actin gene, ACT1, was recently demonstrated to limit but not completely abolish inva...

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Autores principales:	Lisa L. Drewry, L. David Sibley
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2015
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/9d5e63ea242d4877a289a3f8d2bfba98
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spelling	oai:doaj.org-article:9d5e63ea242d4877a289a3f8d2bfba982021-11-15T15:49:03Z<italic toggle="yes">Toxoplasma</italic> Actin Is Required for Efficient Host Cell Invasion10.1128/mBio.00557-152150-7511https://doaj.org/article/9d5e63ea242d4877a289a3f8d2bfba982015-07-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00557-15https://doaj.org/toc/2150-7511ABSTRACT Apicomplexan parasites actively invade host cells using a mechanism predicted to be powered by a parasite actin-dependent myosin motor. In the model apicomplexan Toxoplasma gondii, inducible knockout of the actin gene, ACT1, was recently demonstrated to limit but not completely abolish invasion. This observation has led to the provocative suggestion that T. gondii possesses alternative, ACT1-independent invasion pathways. Here, we dissected the residual invasive ability of Δact1 parasites. Surprisingly, we were able to detect residual ACT1 protein in inducible Δact1 parasites as long as 5 days after ACT1 deletion. We further found that the longer Δact1 parasites were propagated after ACT1 deletion, the more severe an invasion defect was observed. Both findings are consistent with the quantity of residual ACT1 retained in Δact1 parasites being responsible for their invasive ability. Furthermore, invasion by the Δact1 parasites was also sensitive to the actin polymerization inhibitor cytochalasin D. Finally, there was no clear defect in attachment to host cells or moving junction formation by Δact1 parasites. However, Δact1 parasites often exhibited delayed entry into host cells, suggesting a defect specific to the penetration stage of invasion. Overall, our results support a model where residual ACT1 protein retained in inducible Δact1 parasites facilitates their limited invasive ability and confirm that parasite actin is essential for efficient penetration into host cells during invasion. IMPORTANCE The prevailing model for apicomplexan invasion has recently been suggested to require major revision, based on studies where core components of the invasion machinery were genetically disrupted using a Cre-Lox-based inducible knockout system. For the myosin component of the motor thought to power invasion, an alternative parasite myosin was recently demonstrated to functionally compensate for loss of the primary myosin involved in invasion. Here, we highlight a second mechanism that can account for the surprising ability of parasites to invade after genetic disruption of core invasion machinery. Specifically, residual actin protein present in inducible knockout parasites appears able to support their limited invasion of host cells. Our results have important implications for the interpretation of the apicomplexan invasion model and also highlight significant considerations when analyzing the phenotypes of inducible knockout parasites generated using Cre-Lox technology.Lisa L. DrewryL. David SibleyAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 6, Iss 3 (2015)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Lisa L. Drewry L. David Sibley <italic toggle="yes">Toxoplasma</italic> Actin Is Required for Efficient Host Cell Invasion
description	ABSTRACT Apicomplexan parasites actively invade host cells using a mechanism predicted to be powered by a parasite actin-dependent myosin motor. In the model apicomplexan Toxoplasma gondii, inducible knockout of the actin gene, ACT1, was recently demonstrated to limit but not completely abolish invasion. This observation has led to the provocative suggestion that T. gondii possesses alternative, ACT1-independent invasion pathways. Here, we dissected the residual invasive ability of Δact1 parasites. Surprisingly, we were able to detect residual ACT1 protein in inducible Δact1 parasites as long as 5 days after ACT1 deletion. We further found that the longer Δact1 parasites were propagated after ACT1 deletion, the more severe an invasion defect was observed. Both findings are consistent with the quantity of residual ACT1 retained in Δact1 parasites being responsible for their invasive ability. Furthermore, invasion by the Δact1 parasites was also sensitive to the actin polymerization inhibitor cytochalasin D. Finally, there was no clear defect in attachment to host cells or moving junction formation by Δact1 parasites. However, Δact1 parasites often exhibited delayed entry into host cells, suggesting a defect specific to the penetration stage of invasion. Overall, our results support a model where residual ACT1 protein retained in inducible Δact1 parasites facilitates their limited invasive ability and confirm that parasite actin is essential for efficient penetration into host cells during invasion. IMPORTANCE The prevailing model for apicomplexan invasion has recently been suggested to require major revision, based on studies where core components of the invasion machinery were genetically disrupted using a Cre-Lox-based inducible knockout system. For the myosin component of the motor thought to power invasion, an alternative parasite myosin was recently demonstrated to functionally compensate for loss of the primary myosin involved in invasion. Here, we highlight a second mechanism that can account for the surprising ability of parasites to invade after genetic disruption of core invasion machinery. Specifically, residual actin protein present in inducible knockout parasites appears able to support their limited invasion of host cells. Our results have important implications for the interpretation of the apicomplexan invasion model and also highlight significant considerations when analyzing the phenotypes of inducible knockout parasites generated using Cre-Lox technology.
format	article
author	Lisa L. Drewry L. David Sibley
author_facet	Lisa L. Drewry L. David Sibley
author_sort	Lisa L. Drewry
title	<italic toggle="yes">Toxoplasma</italic> Actin Is Required for Efficient Host Cell Invasion
title_short	<italic toggle="yes">Toxoplasma</italic> Actin Is Required for Efficient Host Cell Invasion
title_full	<italic toggle="yes">Toxoplasma</italic> Actin Is Required for Efficient Host Cell Invasion
title_fullStr	<italic toggle="yes">Toxoplasma</italic> Actin Is Required for Efficient Host Cell Invasion
title_full_unstemmed	<italic toggle="yes">Toxoplasma</italic> Actin Is Required for Efficient Host Cell Invasion
title_sort	<italic toggle="yes">toxoplasma</italic> actin is required for efficient host cell invasion
publisher	American Society for Microbiology
publishDate	2015
url	https://doaj.org/article/9d5e63ea242d4877a289a3f8d2bfba98
work_keys_str_mv	AT lisaldrewry italictoggleyestoxoplasmaitalicactinisrequiredforefficienthostcellinvasion AT ldavidsibley italictoggleyestoxoplasmaitalicactinisrequiredforefficienthostcellinvasion
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<italic toggle="yes">Toxoplasma</italic> Actin Is Required for Efficient Host Cell Invasion

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