<italic toggle="yes">Toxoplasma</italic> Cathepsin Protease B and Aspartyl Protease 1 Are Dispensable for Endolysosomal Protein Digestion

ABSTRACT The lysosome-like vacuolar compartment (VAC) is a major site of proteolysis in the intracellular parasite Toxoplasma gondii. Previous studies have shown that genetic ablation of a VAC-residing cysteine protease, cathepsin protease L (CPL), resulted in the accumulation of undigested protein...

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Autores principales:	Christian McDonald, David Smith, Manlio Di Cristina, Geetha Kannan, Zhicheng Dou, Vern B. Carruthers
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	Toxoplasma gondii autophagy cathepsin lysosome proteases Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/f28ca7b56c8f483ca29aa45225b73bdc
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spelling	oai:doaj.org-article:f28ca7b56c8f483ca29aa45225b73bdc2021-11-15T15:27:52Z<italic toggle="yes">Toxoplasma</italic> Cathepsin Protease B and Aspartyl Protease 1 Are Dispensable for Endolysosomal Protein Digestion10.1128/mSphere.00869-192379-5042https://doaj.org/article/f28ca7b56c8f483ca29aa45225b73bdc2020-02-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mSphere.00869-19https://doaj.org/toc/2379-5042ABSTRACT The lysosome-like vacuolar compartment (VAC) is a major site of proteolysis in the intracellular parasite Toxoplasma gondii. Previous studies have shown that genetic ablation of a VAC-residing cysteine protease, cathepsin protease L (CPL), resulted in the accumulation of undigested protein in the VAC and loss of parasite viability during the chronic stage of infection. However, since the maturation of another VAC localizing protease, cathepsin protease B (CPB), is dependent on CPL, it remained unknown whether these defects result directly from ablation of CPL or indirectly from a lack of CPB maturation. Likewise, although a previously described cathepsin D-like aspartyl protease 1 (ASP1) could also play a role in proteolysis, its definitive residence and function in the Toxoplasma endolysosomal system were not well defined. Here, we demonstrate that CPB is not necessary for protein turnover in the VAC and that CPB-deficient parasites have normal growth and viability in both the acute and chronic stages of infection. We also show that ASP1 depends on CPL for correct maturation, and it resides in the T. gondii VAC, where, similar to CPB, it plays a dispensable role in protein digestion. Taken together with previous work, our findings suggest that CPL is the dominant protease in a hierarchy of proteolytic enzymes within the VAC. This unusual lack of redundancy for CPL in T. gondii makes it a single exploitable target for disrupting chronic toxoplasmosis. IMPORTANCE Roughly one-third of the human population is chronically infected with the intracellular single-celled parasite Toxoplasma gondii, but little is known about how this organism persists inside people. Previous research suggested that a parasite proteolytic enzyme, termed cathepsin protease L, is important for Toxoplasma persistence; however, it remained possible that other associated proteolytic enzymes could also be involved in the long-term survival of the parasite during infection. Here, we show that two proteolytic enzymes associated with cathepsin protease L play dispensable roles and are dependent on cathepsin L to reach maturity, which differs from the corresponding enzymes in humans. These findings establish a divergent hierarchy of proteases and help focus attention principally on cathepsin protease L as a potential target for interrupting Toxoplasma chronic infection.Christian McDonaldDavid SmithManlio Di CristinaGeetha KannanZhicheng DouVern B. CarruthersAmerican Society for MicrobiologyarticleToxoplasma gondiiautophagycathepsinlysosomeproteasesMicrobiologyQR1-502ENmSphere, Vol 5, Iss 1 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	Toxoplasma gondii autophagy cathepsin lysosome proteases Microbiology QR1-502
spellingShingle	Toxoplasma gondii autophagy cathepsin lysosome proteases Microbiology QR1-502 Christian McDonald David Smith Manlio Di Cristina Geetha Kannan Zhicheng Dou Vern B. Carruthers <italic toggle="yes">Toxoplasma</italic> Cathepsin Protease B and Aspartyl Protease 1 Are Dispensable for Endolysosomal Protein Digestion
description	ABSTRACT The lysosome-like vacuolar compartment (VAC) is a major site of proteolysis in the intracellular parasite Toxoplasma gondii. Previous studies have shown that genetic ablation of a VAC-residing cysteine protease, cathepsin protease L (CPL), resulted in the accumulation of undigested protein in the VAC and loss of parasite viability during the chronic stage of infection. However, since the maturation of another VAC localizing protease, cathepsin protease B (CPB), is dependent on CPL, it remained unknown whether these defects result directly from ablation of CPL or indirectly from a lack of CPB maturation. Likewise, although a previously described cathepsin D-like aspartyl protease 1 (ASP1) could also play a role in proteolysis, its definitive residence and function in the Toxoplasma endolysosomal system were not well defined. Here, we demonstrate that CPB is not necessary for protein turnover in the VAC and that CPB-deficient parasites have normal growth and viability in both the acute and chronic stages of infection. We also show that ASP1 depends on CPL for correct maturation, and it resides in the T. gondii VAC, where, similar to CPB, it plays a dispensable role in protein digestion. Taken together with previous work, our findings suggest that CPL is the dominant protease in a hierarchy of proteolytic enzymes within the VAC. This unusual lack of redundancy for CPL in T. gondii makes it a single exploitable target for disrupting chronic toxoplasmosis. IMPORTANCE Roughly one-third of the human population is chronically infected with the intracellular single-celled parasite Toxoplasma gondii, but little is known about how this organism persists inside people. Previous research suggested that a parasite proteolytic enzyme, termed cathepsin protease L, is important for Toxoplasma persistence; however, it remained possible that other associated proteolytic enzymes could also be involved in the long-term survival of the parasite during infection. Here, we show that two proteolytic enzymes associated with cathepsin protease L play dispensable roles and are dependent on cathepsin L to reach maturity, which differs from the corresponding enzymes in humans. These findings establish a divergent hierarchy of proteases and help focus attention principally on cathepsin protease L as a potential target for interrupting Toxoplasma chronic infection.
format	article
author	Christian McDonald David Smith Manlio Di Cristina Geetha Kannan Zhicheng Dou Vern B. Carruthers
author_facet	Christian McDonald David Smith Manlio Di Cristina Geetha Kannan Zhicheng Dou Vern B. Carruthers
author_sort	Christian McDonald
title	<italic toggle="yes">Toxoplasma</italic> Cathepsin Protease B and Aspartyl Protease 1 Are Dispensable for Endolysosomal Protein Digestion
title_short	<italic toggle="yes">Toxoplasma</italic> Cathepsin Protease B and Aspartyl Protease 1 Are Dispensable for Endolysosomal Protein Digestion
title_full	<italic toggle="yes">Toxoplasma</italic> Cathepsin Protease B and Aspartyl Protease 1 Are Dispensable for Endolysosomal Protein Digestion
title_fullStr	<italic toggle="yes">Toxoplasma</italic> Cathepsin Protease B and Aspartyl Protease 1 Are Dispensable for Endolysosomal Protein Digestion
title_full_unstemmed	<italic toggle="yes">Toxoplasma</italic> Cathepsin Protease B and Aspartyl Protease 1 Are Dispensable for Endolysosomal Protein Digestion
title_sort	<italic toggle="yes">toxoplasma</italic> cathepsin protease b and aspartyl protease 1 are dispensable for endolysosomal protein digestion
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/f28ca7b56c8f483ca29aa45225b73bdc
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<italic toggle="yes">Toxoplasma</italic> Cathepsin Protease B and Aspartyl Protease 1 Are Dispensable for Endolysosomal Protein Digestion

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