Publications (21)154.37 Total impact
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Article: Structural features affecting trafficking, processing, and secretion of Trypanosoma cruzi mucins.
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ABSTRACT: Trypanosoma cruzi is wrapped by a dense coat of mucin-type molecules encoded by complex gene families termed TcSMUG and TcMUC, which are expressed in the insect- and mammal-dwelling forms of the parasite, respectively. Here, we dissect the contribution of distinct post-translational modifications on the trafficking of these glycoconjugates. In vivo tracing and characterization of tagged-variants expressed by transfected epimastigotes indicate that although the N-terminal signal peptide is responsible for targeting TcSMUG products to the endoplasmic reticulum (ER), the glycosyl phosphatidylinositol (GPI)-anchor likely functions as a forward transport signal for their timely progression along the secretory pathway. GPI-minus variants accumulate in the ER, with only a minor fraction being ultimately released to the medium as anchorless products. Secreted products, but not ER-accumulated ones, display several diagnostic features of mature mucin-type molecules including extensive O-type glycosylation, Galf-based epitopes recognized by monoclonal antibodies, and terminal Galp residues that become readily sialylated upon addition of parasite trans-sialidases. Processing of N-glycosylation site(s) is dispensable for the overall TcSMUG mucin-type maturation and secretion. Despite undergoing different O-glycosylation elaboration, TcMUC reporters yielded quite similar results, thus indicating that (i) molecular trafficking signals are structurally and functionally conserved between mucin families, and (ii) TcMUC and TcSMUG products are recognized and processed by a distinct repertoire of stage-specific glycosyltransferases. Thus, using the fidelity of a homologous expression system, we have defined some biosynthetic aspects of T. cruzi mucins, key molecules involved in parasite protection and virulence.Journal of Biological Chemistry 06/2012; 287(31):26365-76. · 4.77 Impact Factor -
Article: Evaluation of a recombinant Trypanosoma cruzi mucin-like antigen for serodiagnosis of Chagas' disease.
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ABSTRACT: Chagas' disease is caused by the protozoan parasite Trypanosoma cruzi and is one of the most important endemic problems in Latin America. Lately, it has also become a health concern in the United States and Europe. Currently, a diagnosis of Chagas' disease and the screening of blood supplies for antiparasite antibodies are achieved by conventional serological tests that show substantial variation in the reproducibility and reliability of their results. In addition, the specificity of these assays is curtailed by antigenic cross-reactivity with sera from patients affected by other endemic diseases, such as leishmaniasis. Here we used a highly sensitive chemiluminescent enzyme-linked immunosorbent assay (CL-ELISA) to evaluate a recombinant protein core of a mucin-like molecule (termed trypomastigote small surface antigen [TSSA]) for the detection of specific serum antibodies in a broad panel of human sera. The same samples were evaluated by CL-ELISA using as the antigen either a mixture of native T. cruzi trypomastigote mucins or an epimastigote extract and, for further comparison, by conventional serologic tests, such as an indirect hemagglutination assay and indirect immunofluorescence assay. TSSA showed ∼87% sensitivity among the seropositive Chagasic panel, a value which was increased up to >98% when only parasitologically positive samples were considered. More importantly, TSSA showed a significant increase in specificity (97.4%) compared to those of currently used assays, which averaged 80 to 90%. Overall, our data demonstrate that recombinant TSSA may be a useful antigen for the immunodiagnosis of Chagas' disease.Clinical and vaccine immunology: CVI 08/2011; 18(11):1850-5. · 2.37 Impact Factor -
Article: Molecular diversity of the Trypanosoma cruzi TcSMUG family of mucin genes and proteins.
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ABSTRACT: The surface of the protozoan Trypanosoma cruzi is covered by a dense coat of mucin-type glycoconjugates, which make a pivotal contribution to parasite protection and host immune evasion. Their importance is further underscored by the presence of >1000 mucin-like genes in the parasite genome. In the present study we demonstrate that one such group of genes, termed TcSMUG L, codes for previously unrecognized mucin-type glycoconjugates anchored to and secreted from the surface of insect-dwelling epimastigotes. These features are supported by the in vivo tracing and characterization of endogenous TcSMUG L products and recombinant tagged molecules expressed by transfected parasites. Besides displaying substantial homology to TcSMUG S products, which provide the scaffold for the major Gp35/50 mucins also present in insect-dwelling stages of the T. cruzi lifecycle, TcSMUG L products display unique structural and functional features, including being completely refractory to sialylation by parasite trans-sialidases. Although quantitative real time-PCR and gene sequencing analyses indicate a high degree of genomic conservation across the T. cruzi species, TcSMUG L product expression and processing is quite variable among different parasite isolates.Biochemical Journal 06/2011; 438(2):303-13. · 4.90 Impact Factor -
Article: Plasmodium circumsporozoite protein promotes the development of the liver stages of the parasite.
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ABSTRACT: The liver stages of malaria are clinically silent but have a central role in the Plasmodium life cycle. Liver stages of the parasite containing thousands of merozoites grow inside hepatocytes for several days without triggering an inflammatory response. We show here that Plasmodium uses a PEXEL/VTS motif to introduce the circumsporozoite (CS) protein into the hepatocyte cytoplasm and a nuclear localization signal (NLS) to enter its nucleus. CS outcompetes NFkappaB nuclear import, thus downregulating the expression of many genes controlled by NFkappaB, including those involved in inflammation. CS also influences the expression of over one thousand host genes involved in diverse metabolic processes to create a favorable niche for the parasite growth. The presence of CS in the hepatocyte enhances parasite growth of the liver stages in vitro and in vivo. These findings have far reaching implications for drug and vaccine development against the liver stages of the malaria parasite.Cell 12/2007; 131(3):492-504. · 32.40 Impact Factor -
Article: Aldolase provides an unusual binding site for thrombospondin-related anonymous protein in the invasion machinery of the malaria parasite.
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ABSTRACT: An actomyosin motor located underneath the plasma membrane drives motility and host-cell invasion of apicomplexan parasites such as Plasmodium falciparum and Plasmodium vivax, the causative agents of malaria. Aldolase connects the motor actin filaments to transmembrane adhesive proteins of the thrombospondin-related anonymous protein (TRAP) family and transduces the motor force across the parasite surface. The TRAP-aldolase interaction is a distinctive and critical trait of host hepatocyte invasion by Plasmodium sporozoites, with a likely similar interaction crucial for erythrocyte invasion by merozoites. Here, we describe 2.4-A and 2.7-A structures of P. falciparum aldolase (PfAldo) obtained from crystals grown in the presence of the C-terminal hexapeptide of TRAP from Plasmodium berghei. The indole ring of the critical penultimate Trp-residue of TRAP fits snugly into a newly formed hydrophobic pocket, which is exclusively delimited by hydrophilic residues: two arginines, one glutamate, and one glutamine. Comparison with the unliganded PfAldo structure shows that the two arginines adopt new side-chain rotamers, whereas a 25-residue subdomain, forming a helix-loop-helix unit, shifts upon binding the TRAP-tail. The structural data are in agreement with decreased TRAP binding after mutagenesis of PfAldo residues in and near the induced TRAP-binding pocket. Remarkably, the TRAP- and actin-binding sites of PfAldo seem to overlap, suggesting that both the plasticity of the aldolase active-site region and the multimeric nature of the enzyme are crucial for its intriguing nonenzymatic function in the invasion machinery of the malaria parasite.Proceedings of the National Academy of Sciences 04/2007; 104(17):7015-20. · 9.68 Impact Factor -
Article: Modeling the interaction between aldolase and the thrombospondin-related anonymous protein, a key connection of the malaria parasite invasion machinery.
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ABSTRACT: A complex molecular motor empowers substrate-dependent motility and host cell invasion in malaria parasites. The interaction between aldolase and the transmembrane adhesin thrombospondin-related anonymous protein (TRAP) transduces the motor force across the parasite surface. Here, we analyzed this interaction by using state-of-the-art flexible docking. Besides algorithms to account for induced fit in the side-chains of the Plasmodium falciparum aldolase (PfAldo) structure, we used additional in silico receptors modeled upon crystallographic structures of evolutionarily related aldolases to incorporate enzyme backbone flexibility, and to overcome structure inaccuracies due to the relatively low resolution (3.0 A) of the genuine PfAldo structure. Our results indicate that, in spite of multiple intermolecular contacts, only the six C-terminal residues of the TRAP cytoplasmic tail bind in an ordered manner to PfAldo. This portion of TRAP targets the PfAldo active site, with its n-1 Trp residue, which is essential for this interaction, buried within the PfAldo catalytic pocket. Docking of a TRAP peptide bearing a Trp to Ala mutation rendered the lower energy configurations either bound weakly outside the active site or not bound to PfAldo at all. The position of the bound TRAP peptide, and particularly the close proximity between the carbonyl of its n-2 Asp residue and the experimentally determined position of the phosphate-6 group of fructose 1,6-phosphate bound to mammalian aldolases, predicts an inhibitory effect of TRAP on catalysis. Enzymatic and TRAP-binding assays using mutant PfAldo molecules strongly support the overall structural model. These results might provide the initial framework for the identification of novel antiparasitic compounds.Proteins Structure Function and Bioinformatics 03/2007; 66(3):528-37. · 3.39 Impact Factor -
Article: Trypanosoma cruzi surface mucins: host-dependent coat diversity.
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ABSTRACT: The surface of the protozoan parasite Trypanosoma cruzi is covered in mucins, which contribute to parasite protection and to the establishment of a persistent infection. Their importance is highlighted by the fact that the approximately 850 mucin-encoding genes comprise approximately 1% of the parasite genome and approximately 6% of all predicted T. cruzi genes. The coordinate expression of a large repertoire of mucins containing variable regions in the mammal-dwelling stages of the T. cruzi life cycle suggests a possible strategy to thwart the host immune response. Here, we discuss the expression profiling of T. cruzi mucins, the mechanisms leading to the acquisition of mucin diversity and the possible consequences of a mosaic surface coat in the interplay between parasite and host.Nature Reviews Microbiology 04/2006; 4(3):229-36. · 21.18 Impact Factor -
Article: Immunocharacterization of the mucin-type proteins from the intracellular stage of Trypanosoma cruzi.
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ABSTRACT: The surface of Trypanosoma cruzi is covered by different groups of mucins that are differentially expressed during the parasite life cycle. We have previously identified the major mucins from the bloodstream trypomastigote stage. Here, we present additional evidence that together with our previous observations allows for the identification of a second mucin group also expressed in the mammal-dwelling stages, but predominant in the intracellular amastigote. These mucins are encoded by many genes, are mostly composed of tandem repeats and are highly conserved except for an exposed hypervariable (HV) N-terminal peptide. Antibodies against HV-peptides are restricted to approximately 50% of the chronically infected human population, are monospecific (i.e. directed towards a single HV), and display low-avidity. In contrast, immunization with a single HV-peptide triggers high-avidity, cross-reacting humoral responses against multiple HV sequences, but not against other T. cruzi surface antigens. The diversity present in the HV regions and the characteristics of the antibody response against them suggest a role of these molecules in eluding and/or modulating the mammalian host immune system.Microbes and Infection 03/2006; 8(2):401-9. · 3.10 Impact Factor -
Article: Characterization of an aldolase-binding site in the Wiskott-Aldrich syndrome protein.
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ABSTRACT: The thrombospondin-related anonymous protein (TRAP) is an essential transmembrane molecule in Plasmodium sporozoites. TRAP displays adhesive motifs on the extracellular portion, whereas its cytoplasmic tail connects to actin via aldolase, thus driving parasite motility and host cell invasion. The minimal requirements for the TRAP binding to aldolase were scanned here and found to be shared by different human proteins, including the Wiskott-Aldrich syndrome protein (WASp) family members. In vitro and in vivo binding of WASp members to aldolase was characterized by biochemical, deletion mapping, mutagenesis, and co-immunoprecipitation studies. As in the case of TRAP, the binding of WASp to aldolase is competitively inhibited by the enzyme substrate/products. Furthermore, TRAP and WASp, but not other unrelated aldolase binders, compete for the binding to the enzyme in vitro. Together, our results define a conserved aldolase binding motif in the WASp family members and suggest that aldolase modulates the motility and actin dynamics of mammalian cells. These findings along with the presence of similar aldolase binding motifs in additional human proteins, some of which indeed interact with aldolase in pull-down assays, suggest supplementary, non-glycolytic roles for this enzyme.Journal of Biological Chemistry 02/2006; 281(3):1324-31. · 4.77 Impact Factor -
Article: Differential expression of a virulence factor, the trans-sialidase, by the main Trypanosoma cruzi phylogenetic lineages.
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ABSTRACT: The clinical outcome of Chagas disease is highly variable, mainly because of the heterogeneity of Trypanosoma cruzi, a parasite for which 2 major phylogenetic groups (I and II) were recently defined. Epidemiological and immunological data indicate that the prevalence of T. cruzi II in patients living in the southern cone of South America correlates with the alterations caused by Chagas disease. We report here that infection with T. cruzi II isolates induces 100% mortality in mice, in contrast to infection with T. cruzi I isolates, in which almost all mice enter the chronic phase even when a 1000-fold higher inoculum is administered. Trypomastigotes from T. cruzi II strains express and shed significantly higher amounts of trans-sialidase than do those from the T. cruzi I lineage. Disorganization of the thymus histoarchitecture associated with the circulating enzyme was observed after infection with T. cruzi II strains, in contrast to transient thymus lesions found in mice infected with T. cruzi I strains. Therefore, trans-sialidase becomes the first T. cruzi virulence factor identified that is differentially expressed by the main parasite groups and that contributes to their contrasting behaviors.The Journal of Infectious Diseases 07/2004; 189(12):2250-9. · 6.41 Impact Factor -
Article: The surface coat of the mammal-dwelling infective trypomastigote stage of Trypanosoma cruzi is formed by highly diverse immunogenic mucins.
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ABSTRACT: A thick coat of mucin-like glycoproteins covers the surface of Trypanosoma cruzi and plays a crucial role in parasite protection and infectivity and host immunomodulation. The appealing candidate genes coding for the mucins of the mammal-dwelling stages define a heterogeneous family termed TcMUC, which comprises up to 700 members, thus precluding a genetic approach to address the protein core identity. Here, we demonstrate by multiple approaches that the TcMUC II genes code for the majority of trypomastigote mucins. These molecules display a variable, non-repetitive, highly O-glycosylated central domain, followed by a short conserved C terminus and a glycosylphosphatidylinositol anchor. A simultaneous expression of multiple TcMUC II gene products was observed. Moreover, the C terminus of TcMUC II mucins, but not their central domain, elicited strong antibody responses in patients with Chagas' disease and T. crusi infected animals. This highly diverse coat of mucins may represent a refined parasite strategy to elude the mammalian host immune system.Journal of Biological Chemistry 05/2004; 279(16):15860-9. · 4.77 Impact Factor -
Article: Plasmodium sporozoite molecular cell biology.
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ABSTRACT: Plasmodium sporozoites display complex phenotypes including gliding motility and invasion of and transmigration through cells in the mosquito vector and the vertebrate host. Sporozoite studies have been difficult to perform because of technical concerns. Nevertheless, they have already provided insights into several aspects of sporozoite biology, shared in part with other apicomplexan invasive stages. Structure/function analysis of the thrombospondin-related anonymous protein paved the way to the understanding of the molecular mechanisms of apicomplexan gliding motility and host cell invasion. Functional studies of circumsporozoite protein revealed its role in Plasmodium sporozoite morphogenesis in addition to its well-known function in host cell invasion. Transcriptional surveys, which facilitate the investigation of gene expression programs that control sporozoite phenotypes, have revealed a high degree of previously unappreciated complexity and novel proteins that mediate sporozoite host cell infection.Annual Review of Cell and Developmental Biology 02/2004; 20:29-59. · 15.84 Impact Factor -
Article: Apicomplexan gliding motility and host cell invasion: overhauling the motor model.
Trends in Parasitology 02/2004; 20(1):13-6. · 5.14 Impact Factor -
Article: Differential accumulation of mutations localized in particular domains of the mucin genes expressed in the vertebrate host stage of Trypanosoma cruzi.
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ABSTRACT: The surface of Trypanosoma cruzi is covered by mucin-type glycoproteins involved in parasite protection, attachment and immunoevasion. The gene family coding for the mucins expressed by the parasite in the vertebrate host, named TcMUC, is composed of several hundred members and presents high variability. The genes encoding mucins expressed in the insect-dwelling parasite stages are part of a much more homogeneous family, named TcSMUG. Here, we addressed the organization and evolution of physically linked T. cruzi mucin genes by sequencing large chromosomal fragments containing these genes. Specific accumulation of mutations was restricted to particular domains of TcMUC genes, showing that these regions have, or have had, an accelerated evolution rate. Sequence analysis of several TcMUC genes allowed for the identification of members sharing features of TcMUC I and II, thus evidencing that one group of genes was generated from the other. The highly conserved intergenic regions of both TcMUC and TcSMUG families contained TG-rich microsatellites that were not present in unrelated genes in the cosmids, suggesting a role for homologous recombination in shuffling and/or amplification of T. cruzi mucin genes. The comparison of putative homologous TcMUC II genes from different strains of T. cruzi showed that their central variable domains are conserved. This conservation was always higher at the DNA level suggesting positive selection in these particular regions of TcMUC II genes.Molecular and Biochemical Parasitology 02/2004; 133(1):81-91. · 2.55 Impact Factor -
Article: Improving protein pharmacokinetics by genetic fusion to simple amino acid sequences.
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ABSTRACT: The role of primary amino acid sequences in protein pharmacokinetics, an issue of relevance in both basic knowledge and biotechnology, was addressed here using as a starting point two repetitive antigens from the hemoflagellate Trypanosoma cruzi that are known to stabilize their associated proteins in the bloodstream. A major drawback to their pharmacological application is that these repetitive sequences are highly immunogenic, being therefore the deletion of this characteristic desirable. Based on sequence homology and epitope mapping analyses, an artificial repetitive sequence (PSTAD) was engineered. This motif was tested by genetic fusion to the C terminus of both the trypanosomal trans-sialidase and the rat tyrosine aminotransferase and found to produce a 4.5-6-fold increase in the half-life of the associated proteins in blood while displaying significantly lower immunogenicity. Residues involved in the stabilizing properties of the novel peptide were mapped by a site-directed mutagenesis approach, allowing us to successfully identify another two motifs. Searching databases for sequences displaying some homology, embedded in proline frameworks and associated to shed virulence factors from unrelated microorganisms, resulted in the identification of four other protein extensions. Remarkably, three of them (from Streptococcus pneumoniae, Actinomyces viscosus, and Escherichia coli) revealed similar pharmacokinetic features, suggesting therefore an analogous evolutionarily acquired mechanism to ensure the biodistribution of their corresponding proteins. Our findings indicate that the insertion of defined motifs into a proline-rich framework constitutes a suitable alternative to construct a chimeric protein with extended half-life in blood.Journal of Biological Chemistry 02/2004; 279(5):3375-81. · 4.77 Impact Factor -
Article: Sites of interaction between aldolase and thrombospondin-related anonymous protein in plasmodium.
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ABSTRACT: Gliding motility and host cell invasion by apicomplexan parasites are empowered by an acto-myosin motor located underneath the parasite plasma membrane. The motor is connected to host cell receptors through trans-membrane invasins belonging to the thrombospondin-related anonymous protein (TRAP) family. A recent study indicates that aldolase bridges the cytoplasmic tail of MIC2, the homologous TRAP protein in Toxoplasma, and actin. Here, we confirm these unexpected findings in Plasmodium sporozoites and identify conserved features of the TRAP family cytoplasmic tail required to bind aldolase: a subterminal tryptophan residue and two noncontiguous stretches of negatively charged amino acids. The aldolase substrate and other compounds that bind to the active site inhibit its interaction with TRAP and with F-actin, suggesting that the function of the motor is metabolically regulated. Ultrastructural studies in salivary gland sporozoites localize aldolase to the periphery of the secretory micronemes containing TRAP. Thus, the interaction between aldolase and the TRAP tail takes place during or preceding the biogenesis of the micronemes. The release of their contents in the anterior pole of the parasite upon contact with the target cells should bring simultaneously aldolase, TRAP and perhaps F-actin to the proper subcellular location where the motor is engaged.Molecular Biology of the Cell 01/2004; 14(12):4947-57. · 4.94 Impact Factor -
Article: Trypanosoma cruzi clonal diversity and the epidemiology of Chagas' disease.
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ABSTRACT: Chagas' disease is caused by the protozoan Trypanosoma cruzi and it has a variable clinical outcome. The basis for this variability relies in part on the complexity of the parasite population consisting of multiple clones displaying distinct biological properties. A major current challenge is to correlate parasite genetic variability with pathogenesis.Microbes and Infection 05/2003; 5(5):419-27. · 3.10 Impact Factor -
Article: A functional network of intramolecular cross-reacting epitopes delays the elicitation of neutralizing antibodies to Trypanosoma cruzi trans-sialidase.
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ABSTRACT: Trypanosoma cruzi trans-sialidase (TS) constitutes a key molecule in both the establishment of the infection and in the development of pathologic abnormalities associated with Chagas disease. Several cross-reactive epitopes located in its catalytic region were previously identified. In the present study, a panel of enzymes altered in these epitopes were generated to analyze their in vivo significance. Although displaying similar specific activity, thermal stability, and overall antigenic structure, mutant TS proteins elicited an improved neutralizing response, compared with that in the parent, wild-type molecule. These features support an in vivo role for cross-reactive epitopes in dampening the elicitation of TS-neutralizing antibodies. Structural and immunological evidence indicating that the epitope cross-reactivity could be extended to the highly immunogenic SAPA repeats located on the TS C terminus is also reported. This complex cross-reactive epitope cargo might represent a novel strategy, providing secreted virulence factors with the ability to delay an effective elicitation of humoral response.The Journal of Infectious Diseases 09/2002; 186(3):397-404. · 6.41 Impact Factor -
Article: A Trypanosoma cruzi small surface molecule provides the first immunological evidence that Chagas' disease is due to a single parasite lineage.
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ABSTRACT: Chagas' disease is a major health and economic problem caused by the protozoan Trypanosoma cruzi. Multiple independently evolving clones define a complex parasite population that can be arranged into two broad genetic lineages termed T. cruzi I and II. These lineages have different evolutionary origin and display distinct ecological and biological traits. Here we describe a novel molecule termed TSSA for trypomastigote small surface antigen that provides the first immunological marker allowing discrimination between lineages. TSSA is a surface, glycosylphosphatidyl inositol (GPI)-anchored mucin-like protein, highly antigenic during the infection. TSSA sequences from different parasite isolates reveal a population dimorphism that perfectly matches with the two T. cruzi lineages. Interestingly, this dimorphism is restricted to the central region of the molecule, which comprises the immunodominant B cell epitopes. This sequence variability has a major impact on TSSA antigenicity, leading to no immunological cross-reactivity between both isoforms for antibodies present either in immunization or infection sera. Furthermore, the absolute seroprevalence for TSSA in confirmed Chagasic patients is restricted to T. cruzi II isoform, strongly suggesting that human infections are due to this particular subgroup. Even though association of T. cruzi II with Chagas' disease has been proposed based on molecular markers, this is the first immunological evidence supporting this hypothesis. The implications of these results for the future research on Chagas' disease could be envisaged.Journal of Experimental Medicine 03/2002; 195(4):401-13. · 13.85 Impact Factor -
Article: anonymous protein (TRAP) in Plasmodium
Top co-authors
Top Journals
Institutions
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2011
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University of São Paulo
- Department of Parasitology (ICB)
São Paulo, Estado de Sao Paulo, Brazil
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2004–2011
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National University of General San Martín
- Instituto de Investigaciones Biotecnológicas (IIB-INTECH)
San Martín, Provincia de San Juan, Argentina -
Seattle Institute for Biomedical and Clinical Research
Seattle, WA, USA
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2003–2007
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New York University USA
- Department of Pathology
New York City, NY, USA
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2002
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Instituto de Investigaciones BiotInstituto Tecnológico de Chascomúsecnológicas- Instituto Tecnológico de Chascomús
Buenos Aires, Buenos Aires F.D., Argentina
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