<i>T</i><i>oxoplasma</i>exports dense granule proteins beyond the vacuole to the host cell nucleus and rewires the host genome expression

Bougdour, Alexandre; Tardieux, Isabelle; Hakimi, Mohamed‐Ali

doi:10.1111/cmi.12255

Cited by 59 publications

(59 citation statements)

References 69 publications

(92 reference statements)

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“…For example, GRA15, GRA16, and GRA24 are "unconventional" GRA proteins as they secreted beyond the PV membrane (ϳ16 to 32 h p.i.) and targeted to the host nucleus to reprogram host cell activities (68). GRA22 expression peaks at the sporozoite stage, and this protein also functions as a regulator of T. gondii egress (69), which together with TgLCAT establishes an unanticipated role for dense granules in the control of Toxoplasma exit from host cells.…”

Section: Discussionmentioning

confidence: 99%

A Lipolytic Lecithin:Cholesterol Acyltransferase Secreted by Toxoplasma Facilitates Parasite Replication and Egress

Pszenny

Ehrenman

Romano

et al. 2016

Journal of Biological Chemistry

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The protozoan parasite Toxoplasma gondii develops within a parasitophorous vacuole (PV) in mammalian cells, where it scavenges cholesterol. When cholesterol is present in excess in its environment, the parasite expulses this lipid into the PV or esterifies it for storage in lipid bodies. Here, we characterized a unique T. gondii homologue of mammalian lecithin:cholesterol acyltransferase (LCAT), a key enzyme that produces cholesteryl esters via transfer of acyl groups from phospholipids to the 3-OH of free cholesterol, leading to the removal of excess cholesterol from tissues. TgLCAT contains a motif characteristic of serine lipases "AHSLG" and the catalytic triad consisting of serine, aspartate, and histidine (SDH) from LCAT enzymes. TgL-CAT is secreted by the parasite, but unlike other LCAT enzymes it is cleaved into two proteolytic fragments that share the residues of the catalytic triad and need to be reassembled to reconstitute enzymatic activity. TgLCAT uses phosphatidylcholine as substrate to form lysophosphatidylcholine that has the potential to disrupt membranes. The released fatty acid is transferred to cholesterol, but with a lower transesterification activity than mammalian LCAT. TgLCAT is stored in a subpopulation of dense granule secretory organelles, and following secretion, it localizes to the PV and parasite plasma membrane. LCAT-null parasites have impaired growth in vitro, reduced virulence in animals, and exhibit delays in egress from host cells. Parasites overexpressing LCAT show increased virulence and faster egress. These observations demonstrate that TgLCAT influences the outcome of an infection, presumably by facilitating replication and egress depending on the developmental stage of the parasite.The phospholipase A 2 (PLA 2 ) 2 family of serine lipases comprises more than 30 enzymes in mammals. The PLA 2 members hydrolyze the sn-2 ester of phospholipids, yielding lysophospholipid and releasing a fatty acid (1). Approximately one-third of the PLA 2 family members are secreted from cells and display various localizations post-secretion, reflecting their specialized biological functions (2). Among the secretory PLA 2 , lecithin: cholesterol acyltransferase (LCAT; EC 2.3.1.43) is characterized by dual activity, PLA 2 and acyltransferase. In mammals, this enzyme catalyzes the transacylation of the sn-2 fatty acid liberated from various phospholipids (e.g. phosphatidylcholine or phosphatidylethanolamine) to the 3-␤-hydroxyl group on the A-ring of cholesterol, thereby forming cholesteryl esters (3-5). The primary sequence of LCAT is well conserved between mammalian species (6). A structural model for LCAT predicts the conformation of a catalytic triad formed by SerAsp-His residues involved in the phospholipase reaction (7). Mammalian LCATs are primarily expressed in the liver and secreted to the plasma where they circulate in association with HDL (8). These enzymes are components of the reverse cholesterol transport pathway by which cholesterol from peripheral cells is delivered to the liver f...

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Section: Discussionmentioning

confidence: 99%

A Lipolytic Lecithin:Cholesterol Acyltransferase Secreted by Toxoplasma Facilitates Parasite Replication and Egress

Pszenny

Ehrenman

Romano

et al. 2016

Journal of Biological Chemistry

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“…Transcripts encoding other well-characterized tachyzoite effectors [51,53], namely ROP16, ROP5, and ROP18 were also all expressed at similar levels in both sporozoites and tachyzoites. GRA24, GRA16, and the newly identified GRA28, have all been shown to localize to the host nucleus [33,79] and all three had a significantly higher expression in infecting sporozoites compared to tachyzoites. Whether these effector proteins localize and function in a similar fashion during infection with sporozoites remains to be studied.…”

Section: Discussionmentioning

confidence: 99%

An in vitro model of intestinal infection reveals a developmentally regulated transcriptome of Toxoplasma sporozoites and a NF-κB-like signature in infected host cells

et al. 2017

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Toxoplasmosis is a zoonotic infection affecting approximately 30% of the world’s human population. After sexual reproduction in the definitive feline host, Toxoplasma oocysts, each containing 8 sporozoites, are shed into the environment where they can go on to infect humans and other warm-blooded intermediate hosts. Here, we use an in vitro model to assess host transcriptomic changes that occur in the earliest stages of such infections. We show that infection of rat intestinal epithelial cells with mature sporozoites primarily results in higher expression of genes associated with Tumor Necrosis Factor alpha (TNFα) signaling via NF-κB. Furthermore, we find that, consistent with their biology, these mature, invaded sporozoites display a transcriptome intermediate between the previously reported day 10 oocysts and that of their tachyzoite counterparts. Thus, this study uncovers novel host and pathogen factors that may be critical for the establishment of a successful intracellular niche following sporozoite-initiated infection.

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“…GRA16 binds to a complex composed of a host deubiquitinase (HAUSP) and a host PP2A phosphatase (79). Together, the components of this complex act to maintain levels of the host p53 protein, which may impact host cell growth and cycle progression and/or proinflammatory responses (79,80). Importantly, deletion of GRA16 severely attenuates the virulence of type II strain parasites.…”

Section: Toxoplasma Regulates Host Cell Nuclear Functionsmentioning

confidence: 99%

Toxoplasma gondii Development of Its Replicative Niche: in Its Host Cell and Beyond

Blader

Koshy

2014

Eukaryot Cell

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b Intracellular pathogens can replicate efficiently only after they manipulate and modify their host cells to create an environment conducive to replication. While diverse cellular pathways are targeted by different pathogens, metabolism, membrane and cytoskeletal architecture formation, and cell death are the three primary cellular processes that are modified by infections. Toxoplasma gondii is an obligate intracellular protozoan that infects ϳ30% of the world's population and causes severe and lifethreatening disease in developing fetuses, in immune-comprised patients, and in certain otherwise healthy individuals who are primarily found in South America. The high prevalence of Toxoplasma in humans is in large part a result of its ability to modulate these three host cell processes. Here, we highlight recent work defining the mechanisms by which Toxoplasma interacts with these processes. In addition, we hypothesize why some processes are modified not only in the infected host cell but also in neighboring uninfected cells.T oxoplasma gondii is a protozoan, obligate intracellular parasite that is considered one of the world's most successful pathogens (1). Multiple factors contribute to this success, including a complex life cycle in which the parasite can be transmitted by both vertical and horizontal means, efficient propagation within both its primary (felines) and intermediate hosts, extensive mechanisms to evade and disarm host immunity, an ability to form chronic lifelong infections in intermediate hosts, and a wide host tropism in which the parasite can infect most nucleated cells of warm-blooded animals (2). Central to most of these factors is that Toxoplasma has developed the means to replicate efficiently within the hostile intracellular environment of its host cell. In this review, we highlight recent data that have shed light on how parasite growth is achieved by the parasite interacting with its host cell to manipulate host signaling cascades, transcription, cell survival pathways, and membrane transport. In addition, we discuss how parasites interact with neighboring host cells and propose how this may contribute to establishing a permissive microenvironment to improve its overall success. In particular, we focus on those processes that are essential for the growth of all parasite strains and we refer readers to recent reviews that highlight how polymorphic parasite molecules contribute to Toxoplasma virulence (3-5). NUTRIENT ACQUISITIONAs an obligate intracellular parasite that resides within a nonfusogenic vacuole, Toxoplasma must satisfy its nutritional needs by scavenging essential nutrients from its host cell. These nutrients include carbon sources (glucose and glutamine) to fuel its energy demands, specific amino acids, lipids, and other nutrients. Below, we discuss each of these and highlight pathways and processes that are unique to the parasite that could serve as novel drug targets (Fig. 1). GLUCOSE AND GLUTAMINE POWER THE PARASITEToxoplasma expresses a full complement of glycolytic and tr...

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Toxoplasmaexports dense granule proteins beyond the vacuole to the host cell nucleus and rewires the host genome expression

Cited by 59 publications

References 69 publications

A Lipolytic Lecithin:Cholesterol Acyltransferase Secreted by Toxoplasma Facilitates Parasite Replication and Egress

A Lipolytic Lecithin:Cholesterol Acyltransferase Secreted by Toxoplasma Facilitates Parasite Replication and Egress

An in vitro model of intestinal infection reveals a developmentally regulated transcriptome of Toxoplasma sporozoites and a NF-κB-like signature in infected host cells

Toxoplasma gondii Development of Its Replicative Niche: in Its Host Cell and Beyond

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