Cathepsin W Is Required for Escape of Influenza A Virus from Late Endosomes

ABSTRACT Human cathepsin W (CtsW) is a cysteine protease, which was identified in a genome-wide RNA interference (RNAi) screen to be required for influenza A virus (IAV) replication. In this study, we show that reducing the levels of expression of CtsW reduces viral titers for different subtypes of...

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Autores principales:	Thomas O. Edinger, Marie O. Pohl, Emilio Yángüez, Silke Stertz
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2015
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/7f7d731e2ec249ff90cbde70d238cb43
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spelling	oai:doaj.org-article:7f7d731e2ec249ff90cbde70d238cb432021-11-15T15:49:02ZCathepsin W Is Required for Escape of Influenza A Virus from Late Endosomes10.1128/mBio.00297-152150-7511https://doaj.org/article/7f7d731e2ec249ff90cbde70d238cb432015-07-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00297-15https://doaj.org/toc/2150-7511ABSTRACT Human cathepsin W (CtsW) is a cysteine protease, which was identified in a genome-wide RNA interference (RNAi) screen to be required for influenza A virus (IAV) replication. In this study, we show that reducing the levels of expression of CtsW reduces viral titers for different subtypes of IAV, and we map the target step of CtsW requirement to viral entry. Using a set of small interfering RNAs (siRNAs) targeting CtsW, we demonstrate that knockdown of CtsW results in a decrease of IAV nucleoprotein accumulation in the nuclei of infected cells at 3 h postinfection. Assays specific for the individual stages of IAV entry further show that attachment, internalization, and early endosomal trafficking are not affected by CtsW knockdown. However, we detected impaired escape of viral particles from late endosomes in CtsW knockdown cells. Moreover, fusion analysis with a dual-labeled influenza virus revealed a significant reduction in fusion events, with no detectable impact on endosomal pH, suggesting that CtsW is required at the stage of viral fusion. The defect in IAV entry upon CtsW knockdown could be rescued by ectopic expression of wild-type CtsW but not by the expression of a catalytically inactive mutant of CtsW, suggesting that the proteolytic activity of CtsW is required for successful entry of IAV. Our results establish CtsW as an important host factor for entry of IAV into target cells and suggest that CtsW could be a promising target for the development of future antiviral drugs. IMPORTANCE Increasing levels of resistance of influenza viruses to available antiviral drugs have been observed. Development of novel treatment options is therefore of high priority. In parallel to the classical approach of targeting viral enzymes, a novel strategy is pursued: cell-dependent factors of the virus are identified with the aim of developing small-molecule inhibitors against a cellular target that the virus relies on. For influenza A virus, several genome-wide RNA interference (RNAi) screens revealed hundreds of potential cellular targets. However, we have only limited knowledge on how these factors support virus replication, which would be required for drug development. We have characterized cathepsin W, one of the candidate factors, and found that cathepsin W is required for escape of influenza virus from the late endosome. Importantly, this required the proteolytic activity of cathepsin W. We therefore suggest that cathepsin W could be a target for future host cell-directed antiviral therapies.Thomas O. EdingerMarie O. PohlEmilio YángüezSilke StertzAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 6, Iss 3 (2015)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Thomas O. Edinger Marie O. Pohl Emilio Yángüez Silke Stertz Cathepsin W Is Required for Escape of Influenza A Virus from Late Endosomes
description	ABSTRACT Human cathepsin W (CtsW) is a cysteine protease, which was identified in a genome-wide RNA interference (RNAi) screen to be required for influenza A virus (IAV) replication. In this study, we show that reducing the levels of expression of CtsW reduces viral titers for different subtypes of IAV, and we map the target step of CtsW requirement to viral entry. Using a set of small interfering RNAs (siRNAs) targeting CtsW, we demonstrate that knockdown of CtsW results in a decrease of IAV nucleoprotein accumulation in the nuclei of infected cells at 3 h postinfection. Assays specific for the individual stages of IAV entry further show that attachment, internalization, and early endosomal trafficking are not affected by CtsW knockdown. However, we detected impaired escape of viral particles from late endosomes in CtsW knockdown cells. Moreover, fusion analysis with a dual-labeled influenza virus revealed a significant reduction in fusion events, with no detectable impact on endosomal pH, suggesting that CtsW is required at the stage of viral fusion. The defect in IAV entry upon CtsW knockdown could be rescued by ectopic expression of wild-type CtsW but not by the expression of a catalytically inactive mutant of CtsW, suggesting that the proteolytic activity of CtsW is required for successful entry of IAV. Our results establish CtsW as an important host factor for entry of IAV into target cells and suggest that CtsW could be a promising target for the development of future antiviral drugs. IMPORTANCE Increasing levels of resistance of influenza viruses to available antiviral drugs have been observed. Development of novel treatment options is therefore of high priority. In parallel to the classical approach of targeting viral enzymes, a novel strategy is pursued: cell-dependent factors of the virus are identified with the aim of developing small-molecule inhibitors against a cellular target that the virus relies on. For influenza A virus, several genome-wide RNA interference (RNAi) screens revealed hundreds of potential cellular targets. However, we have only limited knowledge on how these factors support virus replication, which would be required for drug development. We have characterized cathepsin W, one of the candidate factors, and found that cathepsin W is required for escape of influenza virus from the late endosome. Importantly, this required the proteolytic activity of cathepsin W. We therefore suggest that cathepsin W could be a target for future host cell-directed antiviral therapies.
format	article
author	Thomas O. Edinger Marie O. Pohl Emilio Yángüez Silke Stertz
author_facet	Thomas O. Edinger Marie O. Pohl Emilio Yángüez Silke Stertz
author_sort	Thomas O. Edinger
title	Cathepsin W Is Required for Escape of Influenza A Virus from Late Endosomes
title_short	Cathepsin W Is Required for Escape of Influenza A Virus from Late Endosomes
title_full	Cathepsin W Is Required for Escape of Influenza A Virus from Late Endosomes
title_fullStr	Cathepsin W Is Required for Escape of Influenza A Virus from Late Endosomes
title_full_unstemmed	Cathepsin W Is Required for Escape of Influenza A Virus from Late Endosomes
title_sort	cathepsin w is required for escape of influenza a virus from late endosomes
publisher	American Society for Microbiology
publishDate	2015
url	https://doaj.org/article/7f7d731e2ec249ff90cbde70d238cb43
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Cathepsin W Is Required for Escape of Influenza A Virus from Late Endosomes

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