Toxoplasma gondii: redistribution of tachyzoite surface protein during host cell invasion and intracellular development

Congenital and acquired toxoplasmosis caused by the food- and water-born parasite Toxoplasma gondii (T. gondii) is one of the most prevalent zoonotic infection of global importance. T. gondii is an obligate intracellular parasite with limited capacity for extracellular survival, thus a successful, efficient and robust host cell invasion process is crucial for its survival, proliferation and transmission. In this study, we screened a series of novel 1,3,4-thiadiazole-2-halophenylamines functionalized at the C5 position with the imidazole ring (1b–12b) for their effects on T. gondii host cell invasion and proliferation. To achieve this goal, these compounds were initially subjected to in vitro assays to assess their cytotoxicity on human fibroblasts and then antiparasitic efficacy. Results showed that all of them compare favorably to control drugs sulfadiazine and trimethoprim in terms of T. gondii growth inhibition (IC50) and selectivity toward the parasite, expressed as selectivity index (SI). Subsequently, the most potent of them with meta-fluoro 2b, meta-chloro 5b, meta-bromo 8b, meta-iodo 11b and para-iodo 12b substitution were tested for their efficacy in inhibition of tachyzoites invasion and subsequent proliferation by direct action on established intracellular infection. All the compounds significantly inhibited the parasite invasion and intracellular proliferation via direct action on both tachyzoites and parasitophorous vacuoles formation. The most effective was para-iodo derivative 12b that caused reduction in the percentage of infected host cells by 44% and number of tachyzoites per vacuole by 93% compared to non-treated host cells. Collectively, these studies indicate that 1,3,4-thiadiazoles 1b–12b, especially 12b with IC50 of 4.70 µg/mL and SI of 20.89, could be considered as early hit compounds for future design and synthesis of anti-Toxoplasma agents that effectively and selectively block the invasion and subsequent proliferation of T. gondii into host cells.

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The Putative TCP-1 Chaperonin Is an Important Player Involved in Sialic Acid-Dependent Host Cell Invasion by Toxoplasma gondii

Frontiers in Microbiology ◽

10.3389/fmicb.2020.00258 ◽

2020 ◽

Vol 11 ◽

Author(s):

Na Yang ◽

Mengen Xing ◽

Yingying Ding ◽

Dawei Wang ◽

Xiaogai Guo ◽

...

Keyword(s):

Sialic Acid ◽

Toxoplasma Gondii ◽

Host Cell ◽

Cell Invasion ◽

Host Cell Invasion ◽

Important Player

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Host cell invasion by Toxoplasma gondii

Trends in Microbiology ◽

10.1016/s0966-842x(97)01165-7 ◽

1998 ◽

Vol 6 (1) ◽

pp. 27-30 ◽

Cited By ~ 61

Author(s):

Jean François Dubremetz

Keyword(s):

Toxoplasma Gondii ◽

Host Cell ◽

Cell Invasion ◽

Host Cell Invasion

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MIC6 associates with aldolase in host cell invasion by Toxoplasma gondii

Parasitology Research ◽

10.1007/s00436-009-1401-5 ◽

2009 ◽

Vol 105 (2) ◽

pp. 441-445 ◽

Cited By ~ 20

Author(s):

Bin Zheng ◽

Ai He ◽

Ming Gan ◽

Zhouya Li ◽

Hualiang He ◽

...

Keyword(s):

Toxoplasma Gondii ◽

Host Cell ◽

Cell Invasion ◽

Host Cell Invasion

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Concerted Action of Two Formins in Gliding Motility and Host Cell Invasion by Toxoplasma gondii

PLoS Pathogens ◽

10.1371/journal.ppat.1001132 ◽

2010 ◽

Vol 6 (10) ◽

pp. e1001132 ◽

Cited By ~ 54

Author(s):

Wassim Daher ◽

Fabienne Plattner ◽

Marie-France Carlier ◽

Dominique Soldati-Favre

Keyword(s):

Toxoplasma Gondii ◽

Host Cell ◽

Cell Invasion ◽

Gliding Motility ◽

Host Cell Invasion ◽

Concerted Action

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Not a Simple Tether: Binding of Toxoplasma gondii AMA1 to RON2 during Invasion Protects AMA1 from Rhomboid-Mediated Cleavage and Leads to Dephosphorylation of Its Cytosolic Tail

mBio ◽

10.1128/mbio.00754-16 ◽

2016 ◽

Vol 7 (5) ◽

Cited By ~ 13

Author(s):

Shruthi Krishnamurthy ◽

Bin Deng ◽

Roxana del Rio ◽

Kerry R. Buchholz ◽

Moritz Treeck ◽

...

Keyword(s):

Toxoplasma Gondii ◽

Host Cell ◽

Cell Invasion ◽

Transmembrane Domain ◽

Critical Role ◽

Host Cells ◽

Receptor Protein ◽

Host Cell Invasion ◽

Cell Binding ◽

Apicomplexan Parasites

ABSTRACT Apical membrane antigen 1 (AMA1) is a receptor protein on the surface of Toxoplasma gondii that plays a critical role in host cell invasion. The ligand to which T . gondii AMA1 (TgAMA1) binds, TgRON2, is secreted into the host cell membrane by the parasite during the early stages of invasion. The TgAMA1-TgRON2 complex forms the core of the “moving junction,” a ring-shaped zone of tight contact between the parasite and host cell membranes, through which the parasite pushes itself during invasion. Paradoxically, the parasite also expresses rhomboid proteases that constitutively cleave the TgAMA1 transmembrane domain. How can TgAMA1 function effectively in host cell binding if its extracellular domain is constantly shed from the parasite surface? We show here that when TgAMA1 binds the domain 3 (D3) peptide of TgRON2, its susceptibility to cleavage by rhomboid protease(s) is greatly reduced. This likely serves to maintain parasite-host cell binding at the moving junction, a hypothesis supported by data showing that parasites expressing a hypercleavable version of TgAMA1 invade less efficiently than wild-type parasites do. Treatment of parasites with the D3 peptide was also found to reduce phosphorylation of S527 on the cytoplasmic tail of TgAMA1, and parasites expressing a phosphomimetic S527D allele of TgAMA1 showed an invasion defect. Taken together, these data suggest that TgAMA1-TgRON2 interaction at the moving junction protects TgAMA1 molecules that are actively engaged in host cell penetration from rhomboid-mediated cleavage and generates an outside-in signal that leads to dephosphorylation of the TgAMA1 cytosolic tail. Both of these effects are required for maximally efficient host cell invasion. IMPORTANCE Nearly one-third of the world’s population is infected with the protozoan parasite Toxoplasma gondii , which causes life-threatening disease in neonates and immunocompromised individuals. T. gondii is a member of the phylum Apicomplexa, which includes many other parasites of veterinary and medical importance, such as those that cause coccidiosis, babesiosis, and malaria. Apicomplexan parasites grow within their hosts through repeated cycles of host cell invasion, parasite replication, and host cell lysis. Parasites that cannot invade host cells cannot survive or cause disease. AMA1 is a highly conserved protein on the surface of apicomplexan parasites that is known to be important for invasion, and the work presented here reveals new and unexpected insights into AMA1 function. A more complete understanding of the role of AMA1 in invasion may ultimately contribute to the development of new chemotherapeutics designed to disrupt AMA1 function and invasion-related signaling in this important group of human pathogens.

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A Member of the Ferlin Calcium Sensor Family Is Essential for Toxoplasma gondii Rhoptry Secretion

mBio ◽

10.1128/mbio.01510-18 ◽

2018 ◽

Vol 9 (5) ◽

Cited By ~ 12

Author(s):

Bradley I. Coleman ◽

Sudeshna Saha ◽

Seiko Sato ◽

Klemens Engelberg ◽

David J. P. Ferguson ◽

...

Keyword(s):

Toxoplasma Gondii ◽

Host Cell ◽

Cell Invasion ◽

Host Cells ◽

Model Organisms ◽

Host Cell Invasion ◽

Content Type ◽

Calcium Dependent ◽

Calcium Sensing ◽

Intracellular Ca

ABSTRACT Invasion of host cells by apicomplexan parasites such as Toxoplasma gondii is critical for their infectivity and pathogenesis. In Toxoplasma, secretion of essential egress, motility, and invasion-related proteins from microneme organelles is regulated by oscillations of intracellular Ca2+. Later stages of invasion are considered Ca2+ independent, including the secretion of proteins required for host cell entry and remodeling from the parasite’s rhoptries. We identified a family of three Toxoplasma proteins with homology to the ferlin family of double C2 domain-containing Ca2+ sensors. In humans and model organisms, such Ca2+ sensors orchestrate Ca2+-dependent exocytic membrane fusion with the plasma membrane. Here we focus on one ferlin that is conserved across the Apicomplexa, T. gondii FER2 (TgFER2). Unexpectedly, conditionally TgFER2-depleted parasites secreted their micronemes normally and were completely motile. However, these parasites were unable to invade host cells and were therefore not viable. Knockdown of TgFER2 prevented rhoptry secretion, and these parasites failed to form the moving junction at the parasite-host interface necessary for host cell invasion. Collectively, these data demonstrate the requirement of TgFER2 for rhoptry secretion in Toxoplasma tachyzoites and suggest a possible Ca2+ dependence of rhoptry secretion. These findings provide the first mechanistic insights into this critical yet poorly understood aspect of apicomplexan host cell invasion. IMPORTANCE Apicomplexan protozoan parasites, such as those causing malaria and toxoplasmosis, must invade the cells of their hosts in order to establish a pathogenic infection. Timely release of proteins from a series of apical organelles is required for invasion. Neither the vesicular fusion events that underlie secretion nor the observed reliance of the various processes on changes in intracellular calcium concentrations is completely understood. We identified a group of three proteins with strong homology to the calcium-sensing ferlin family, which are known to be involved in protein secretion in other organisms. Surprisingly, decreasing the amounts of one of these proteins (TgFER2) did not have any effect on the typically calcium-dependent steps in invasion. Instead, TgFER2 was essential for the release of proteins from organelles called rhoptries. These data provide a tantalizing first look at the mechanisms controlling the very poorly understood process of rhoptry secretion, which is essential for the parasite’s infection cycle.

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Genetic Structure and Expression of the Surface Glycoprotein GP82, the Main Adhesin ofTrypanosoma cruziMetacyclic Trypomastigotes

The Scientific World JOURNAL ◽

10.1155/2013/156734 ◽

2013 ◽

Vol 2013 ◽

pp. 1-11 ◽

Cited By ~ 9

Author(s):

Paulo Roberto Ceridorio Correa ◽

Esteban Mauricio Cordero ◽

Luciana Girotto Gentil ◽

Ethel Bayer-Santos ◽

José Franco da Silveira

Keyword(s):

Host Cell ◽

Cell Invasion ◽

Secretory Pathway ◽

Surface Protein ◽

Surface Glycoprotein ◽

Modular Organization ◽

Transcriptional Level ◽

Host Cell Invasion ◽

Mrna Stabilization ◽

Transgenic Parasites

T. cruziimproves the likelihood of invading or adapting to the host through its capacity to present a large repertoire of surface molecules. The metacyclic stage-specific surface glycoprotein GP82 has been implicated in host cell invasion. GP82 is encoded by multiple genes from the trans-sialidase superfamily. GP82 shows a modular organization, with some variation of N-terminal region flanking a conserved central core where the binding sites to the mammalian cell and gastric mucin are located. The function of GP82 as adhesin in host cell invasion process could expose the protein to an intense conservative and selective pressure. GP82 is a GPI-anchored surface protein, synthesized as a 70 kDa precursor devoid ofN-linked sugars. GPI-minus variants accumulate in the ER indicating that GPI anchor acts as a forward transport signal for progressing along the secretory pathway as suggested forT. cruzimucins. It has been demonstrated that the expression of GP82 is constitutive and may be regulated at post-transcriptional level, for instance, at translational level and/or mRNA stabilization. GP82 mRNAs are mobilized to polysomes and consequently translated, but only in metacyclic trypomastigotes. Analysis of transgenic parasites indicates that the mechanism regulating GP82 expression involves multiple elements in the 3′UTR.

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