An Endoplasmic Reticulum CREC Family Protein Regulates the Egress Proteolytic Cascade in Malaria Parasites

ABSTRACT The endoplasmic reticulum (ER) is thought to play an essential role during egress of malaria parasites because the ER is assumed to be required for biogenesis and secretion of egress-related organelles. However, no proteins localized to the parasite ER have been shown to play a role in egre...

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Autores principales:	Manuel A. Fierro, Beejan Asady, Carrie F. Brooks, David W. Cobb, Alejandra Villegas, Silvia N. J. Moreno, Vasant Muralidharan
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	calcium-binding protein malaria Plasmodium egress endoplasmic reticulum Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/e3721d3acf9d446f94b6267c6245c022
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spelling	oai:doaj.org-article:e3721d3acf9d446f94b6267c6245c0222021-11-15T15:56:58ZAn Endoplasmic Reticulum CREC Family Protein Regulates the Egress Proteolytic Cascade in Malaria Parasites10.1128/mBio.03078-192150-7511https://doaj.org/article/e3721d3acf9d446f94b6267c6245c0222020-02-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.03078-19https://doaj.org/toc/2150-7511ABSTRACT The endoplasmic reticulum (ER) is thought to play an essential role during egress of malaria parasites because the ER is assumed to be required for biogenesis and secretion of egress-related organelles. However, no proteins localized to the parasite ER have been shown to play a role in egress of malaria parasites. In this study, we generated conditional mutants of the Plasmodium falciparum endoplasmic reticulum-resident calcium-binding protein (PfERC), a member of the CREC family. Knockdown of the PfERC gene showed that this gene is essential for asexual growth of P. falciparum. Analysis of the intraerythrocytic life cycle revealed that PfERC is essential for parasite egress but is not required for protein trafficking or calcium storage. We found that PfERC knockdown prevents the rupture of the parasitophorous vacuole membrane. This is because PfERC knockdown inhibited the proteolytic maturation of the subtilisin-like serine protease SUB1. Using double mutant parasites, we showed that PfERC is required for the proteolytic maturation of the essential aspartic protease plasmepsin X, which is required for SUB1 cleavage. Further, we showed that processing of substrates downstream of the proteolytic cascade is inhibited by PfERC knockdown. Thus, these data establish that the ER-resident CREC family protein PfERC is a key early regulator of the egress proteolytic cascade of malaria parasites. IMPORTANCE The divergent eukaryotic parasites that cause malaria grow and divide within a vacuole inside a host cell, which they have to break open once they finish cell division. The egress of daughter parasites requires the activation of a proteolytic cascade, and a subtilisin-like protease initiates a proteolytic cascade to break down the membranes blocking egress. It is assumed that the parasite endoplasmic reticulum plays a role in this process, but the proteins in this organelle required for egress remain unknown. We have identified an early ER-resident regulator essential for the maturation of the recently discovered aspartic protease in the egress proteolytic cascade, plasmepsin X, which is required for maturation of the subtilisin-like protease. Conditional loss of PfERC results in the formation of immature and inactive egress proteases that are unable to breakdown the vacuolar membrane barring release of daughter parasites.Manuel A. FierroBeejan AsadyCarrie F. BrooksDavid W. CobbAlejandra VillegasSilvia N. J. MorenoVasant MuralidharanAmerican Society for Microbiologyarticlecalcium-binding proteinmalariaPlasmodiumegressendoplasmic reticulumMicrobiologyQR1-502ENmBio, Vol 11, Iss 1 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	calcium-binding protein malaria Plasmodium egress endoplasmic reticulum Microbiology QR1-502
spellingShingle	calcium-binding protein malaria Plasmodium egress endoplasmic reticulum Microbiology QR1-502 Manuel A. Fierro Beejan Asady Carrie F. Brooks David W. Cobb Alejandra Villegas Silvia N. J. Moreno Vasant Muralidharan An Endoplasmic Reticulum CREC Family Protein Regulates the Egress Proteolytic Cascade in Malaria Parasites
description	ABSTRACT The endoplasmic reticulum (ER) is thought to play an essential role during egress of malaria parasites because the ER is assumed to be required for biogenesis and secretion of egress-related organelles. However, no proteins localized to the parasite ER have been shown to play a role in egress of malaria parasites. In this study, we generated conditional mutants of the Plasmodium falciparum endoplasmic reticulum-resident calcium-binding protein (PfERC), a member of the CREC family. Knockdown of the PfERC gene showed that this gene is essential for asexual growth of P. falciparum. Analysis of the intraerythrocytic life cycle revealed that PfERC is essential for parasite egress but is not required for protein trafficking or calcium storage. We found that PfERC knockdown prevents the rupture of the parasitophorous vacuole membrane. This is because PfERC knockdown inhibited the proteolytic maturation of the subtilisin-like serine protease SUB1. Using double mutant parasites, we showed that PfERC is required for the proteolytic maturation of the essential aspartic protease plasmepsin X, which is required for SUB1 cleavage. Further, we showed that processing of substrates downstream of the proteolytic cascade is inhibited by PfERC knockdown. Thus, these data establish that the ER-resident CREC family protein PfERC is a key early regulator of the egress proteolytic cascade of malaria parasites. IMPORTANCE The divergent eukaryotic parasites that cause malaria grow and divide within a vacuole inside a host cell, which they have to break open once they finish cell division. The egress of daughter parasites requires the activation of a proteolytic cascade, and a subtilisin-like protease initiates a proteolytic cascade to break down the membranes blocking egress. It is assumed that the parasite endoplasmic reticulum plays a role in this process, but the proteins in this organelle required for egress remain unknown. We have identified an early ER-resident regulator essential for the maturation of the recently discovered aspartic protease in the egress proteolytic cascade, plasmepsin X, which is required for maturation of the subtilisin-like protease. Conditional loss of PfERC results in the formation of immature and inactive egress proteases that are unable to breakdown the vacuolar membrane barring release of daughter parasites.
format	article
author	Manuel A. Fierro Beejan Asady Carrie F. Brooks David W. Cobb Alejandra Villegas Silvia N. J. Moreno Vasant Muralidharan
author_facet	Manuel A. Fierro Beejan Asady Carrie F. Brooks David W. Cobb Alejandra Villegas Silvia N. J. Moreno Vasant Muralidharan
author_sort	Manuel A. Fierro
title	An Endoplasmic Reticulum CREC Family Protein Regulates the Egress Proteolytic Cascade in Malaria Parasites
title_short	An Endoplasmic Reticulum CREC Family Protein Regulates the Egress Proteolytic Cascade in Malaria Parasites
title_full	An Endoplasmic Reticulum CREC Family Protein Regulates the Egress Proteolytic Cascade in Malaria Parasites
title_fullStr	An Endoplasmic Reticulum CREC Family Protein Regulates the Egress Proteolytic Cascade in Malaria Parasites
title_full_unstemmed	An Endoplasmic Reticulum CREC Family Protein Regulates the Egress Proteolytic Cascade in Malaria Parasites
title_sort	endoplasmic reticulum crec family protein regulates the egress proteolytic cascade in malaria parasites
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/e3721d3acf9d446f94b6267c6245c022
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An Endoplasmic Reticulum CREC Family Protein Regulates the Egress Proteolytic Cascade in Malaria Parasites

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