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Surface Molecules Released by Trypanosoma cruzi Metacyclic Forms Downregulate Host Cell Invasion.

ABSTRACT: BACKGROUND:The question whether metacylic trypomastigote (MT) forms of different T. cruzi strains differentially release surface molecules, and how they affect host cell invasion, remains to be fully clarified. We addressed that question using T. cruzi strains that differ widely in the ability to invade cells. METHODOLOGY/PRINCIPAL FINDINGS:Metacyclic forms were incubated at 37°C for 1 h in complete D10 medium or in nutrient-deprived PBS containing Ca2+ and Mg2+ (PBS++). The conditioned medium (CM), collected after parasite centrifugation, was used for cell invasion assays and Western blot analysis, using monoclonal antibodies directed to gp82 and gp90, the MT surface molecules that promote and negatively regulate invasion, respectively. CM of poorly invasive G strain (G-CM) contained high amounts of gp90 and gp82, either in vesicles or as soluble molecules. CM of highly invasive CL strain (CL-CM) contained gp90 and gp82 at very low levels. HeLa cells were incubated for 1 h with CL strain MT in D10, in absence or in the presence of G-CM or CL-CM. Parasite invasion was significantly inhibited by G-CM, but not by CL-CM. As G strain MT invasion rate in D10 is very low, assays with this strain were performed in PBS++, which induces invasion-promoting lysosome-spreading. G-CM, but not CL-CM, significantly inhibited G strain internalization, effect that was counteracted by preincubating G-CM with an anti-gp90 monoclonal antibody or anti-gp82 polyclonal antibody that do not recognize live MT. G strain CM generated in PBS++ contained much lower amounts of gp90 and gp82 as compared to CM produced in D10, and exhibited lower inhibitory effect on host cell invasion. CONCLUSION/SIGNIFICANCE:Our data suggest that the surface molecules spontaneously released by MT impair parasite-host cell interaction, gp82 presumably competing with the molecule expressed on MT surface for the host cell receptor, and gp90 further contributing to down modulate invasion.

SUBMITTER: Clemente TM

PROVIDER: S-EPMC4970754 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Surface Molecules Released by Trypanosoma cruzi Metacyclic Forms Downregulate Host Cell Invasion.

Clemente Tatiana Mordente TM Cortez Cristian C Novaes Antônio da Silva Ada S Yoshida Nobuko N

PLoS neglected tropical diseases 20160802 8

<h4>Background</h4>The question whether metacylic trypomastigote (MT) forms of different T. cruzi strains differentially release surface molecules, and how they affect host cell invasion, remains to be fully clarified. We addressed that question using T. cruzi strains that differ widely in the ability to invade cells.<h4>Methodology/principal findings</h4>Metacyclic forms were incubated at 37°C for 1 h in complete D10 medium or in nutrient-deprived PBS containing Ca2+ and Mg2+ (PBS++). The condi ...[more]

PMID: 27483135

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Project description:Host cell invasion is a critical step for infection by Trypanosoma cruzi, the agent of Chagas disease. In natural infection, T. cruzi metacyclic trypomastigote (MT) forms establish the first interaction with host cells. The gp35/50 mucin molecules expressed in MT have been implicated in cell invasion process, but the mechanisms involved are not well understood. We performed a series of experiments to elucidate the mode of gp35/50-mediated MT internalization. Comparing two parasite strains from genetically divergent groups, G strain (TcI) and CL strain (TcVI), expressing variant forms of mucins, we demonstrated that G strain mucins participate in MT invasion. Only G strain-derived mucins bound to HeLa cells in a receptor-dependent manner and significantly inhibited G strain MT invasion. CL strain MT internalization was not affected by mucins from either strain. HeLa cell invasion by G strain MT was associated with actin recruitment and did not rely on lysosome mobilization. To examine the involvement of annexin A2, which plays a role in actin dynamic, annexin A2-depleted HeLa cells were generated. Annexin A2-deficient cell lines were significantly more resistant than wild type controls to G strain MT invasion. In a co-immunoprecipitation assay, to check whether annexin A2 might be the receptor for mucins, protein A/G magnetic beads crosslinked with monoclonal antibody to G strain mucins were incubated with detergent extracts of MT and HeLa cells. Binding of gp35/50 mucins to annexin A2 was detected. Both G strain MT and purified mucins induced focal adhesion kinase activation in HeLa cells. By confocal immunofluorescence microscopy, colocalization of invading G strain MT with clathrin was visualized. Inhibition of clathrin-coated vesicle formation reduced parasite internalization. Taken together, our data indicate that gp35/50-mediated MT invasion is accomplished through interaction with host cell annexin A2 and clathrin-dependent endocytosis. Author summary Host cell invasion by Trypanosoma cruzi, the agent of Chagas disease, is critical for the establishment of infection. Metacyclic trypomastigote (MT) forms are responsible for the initial T. cruzi-host cell interaction. Mucin molecules expressed on MT surface have been implicated in target cell invasion process, but the underlying mechanism are not fully understood. In this study, we aimed at elucidating the mode of mucin-mediated MT internalization. We found that requirement of mucins for MT invasion is T. cruzi strain-dependent. Experiments with G strain MTs, which rely on mucins and on target cell actin for internalization, revealed that mucin molecules bind to annexin A2, a protein that plays a role in actin dynamic. Annexin A2-deficient cell lines were generated and found to be significantly more resistant than wild type controls to MT invasion. Both MT and purified mucins induced focal adhesion kinase activation in host cells. By confocal immunofluorescence microscopy, invading MT was found to colocalize with clathrin, a protein that plays a role in endocytosis. Inhibition of clathrin-coated vesicle formation reduced parasite internalization. From these data we infer that mucin-mediated MT invasion is accomplished through interaction with host cell annexin A2 and clathrin-dependent endocytosis.

Project description:Metacyclic trypomastigote (MT) forms of Trypanosoma cruzi have been shown to release into medium gp82 and gp90, the stage-specific surface molecules that regulate host cell invasion, either in vesicles or in soluble form. Here, we found that during interaction of poorly invasive G strain with the host cell, gp82 and gp90 were released in vesicle-like forms, whereas no such release by highly invasive CL strain was observed. Shedding of vesicles of varying sizes by CL and G strains was visualized by scanning electron microscopy, and the protein profile of conditioned medium (CM) of the two strains was similar, but the content of gp82 and gp90 differed, with both molecules being detected in G strain as bands of high intensity in Western blotting, whereas in CL strain, they were barely detectable. Confocal images revealed a distinct distribution of gp82 and gp90 on MT surface of CL and G strains. In cell invasion assays, addition of G strain CM resulted in decreased CL strain internalization. Depletion of gp82 in G strain CM, by treatment with specific mAb-coupled magnetic beads, increased its inhibitory effect on CL strain invasion, in contrast to CM depleted in gp90. The effect of cholesterol-depleting drug methyl-β-cyclodextrin (MβCD) on gp82 and gp90 release by MTs was also examined. G strain MTs, untreated or treated with MβCD, were incubated in serum-containing medium or in nutrient-depleted PBS++, and the CM generated under these conditions was analyzed by Western blotting. In PBS++, gp82 and gp90 were released at lower levels by untreated MTs, as compared with MβCD-treated parasites. CM from untreated and MβCD-treated G strain, generated in PBS++, inhibited CL strain internalization. Treatment of CL strain MTs with MβCD resulted in increased gp82 and gp90 shedding and in decreased host cell invasion. The involvement of phospholipase C (PLC) on gp82 and gp90 shedding was also investigated. The CM from G strain MTs pretreated with specific PLC inhibitor contained lower levels of gp82 and gp90, as compared with untreated parasites. Our results contribute to shed light on the mechanism by which T. cruzi releases surface molecules implicated in host cell invasion.

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Surface Molecules Released by Trypanosoma cruzi Metacyclic Forms Downregulate Host Cell Invasion.

Publications

Surface Molecules Released by Trypanosoma cruzi Metacyclic Forms Downregulate Host Cell Invasion.

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