Identification of enolase as a plasminogen‐binding protein in excretory–secretory products of <i>Fasciola hepatica</i>

Bernal, Dolores; Rubia, José Enrique De la; Carrasco-Abad, Ana M; Toledo, Rafael; Mas‐Coma, Santiago; Marcilla, Antonio

doi:10.1016/s0014-5793(04)00306-0

Cited by 129 publications

(95 citation statements)

References 35 publications

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“…Neither the function(s) nor the regulation of the surface-localized enolase is understood at present. Cell surface association of enolase is also reported in the case of pathogens such as Streptococci (3,39,40), C. albicans (31,41,55), and other bacteria (4,15,48). Recently, different experimental approaches such as genetic, cellular biology, and proteomic have been used to show that yeast enolase can reach the cell surface (25).…”

Section: Discussionmentioning

confidence: 93%

Protective Properties and Surface Localization ofPlasmodium falciparumEnolase

et al. 2007

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The enolase protein of the human malarial parasite Plasmodium falciparum has recently been characterized. Apart from its glycolytic function, enolase has also been shown to possess antigenic properties and to be present on the cell wall of certain invasive organisms, such as Candida albicans. In order to assess whether enolase of P. falciparum is also antigenic, sera from residents of a region of Eastern India where malaria is endemic were tested against the recombinant P. falciparum enolase (r-Pfen) protein. About 96% of immune adult sera samples reacted with r-Pfen over and above the seronegative controls. Rabbit anti-r-Pfen antibodies inhibited the growth of in vitro cultures of P. falciparum. Mice immunized with r-Pfen showed protection against a challenge with the 17XL lethal strain of the mouse malarial parasite Plasmodium yoelii. The antibodies raised against r-Pfen were specific for Plasmodium and did not react to the host tissues. Immunofluorescence as well as electron microscopic examinations revealed localization of the enolase protein on the merozoite cell surface. These observations establish malaria enolase to be a potential protective antigen.Malaria continues to be a life-threatening infectious disease in the tropical world. Despite tremendous efforts to control the malaria epidemic, current prophylaxis and drug treatments are proving insufficient. The extensive spreading of drug-resistant Plasmodium strains as well as insecticide-resistant mosquitoes makes it urgent to develop an effective malaria vaccine. Long years of antigen identification and characterization have yielded many potential vaccine candidates, but developing an effective malaria vaccine has remained an incredibly difficult challenge (17). It has been observed that immunity to the disease develops gradually, after many attacks and over many years, in adults living in areas where malaria is endemic (2). The successful passive transfer of this immunity by injecting antibodies from malaria-immune persons to children susceptible to malaria has demonstrated that antibodies alone can trigger protection (5, 9, 58). These experiments have worked across geographical borders, as immunoglobulin G (IgG) from malaria-immune West Africans have cured East Africans as well as Thai malaria patients (5). The nature of this immunity is poorly understood at the molecular level. However, attempts have been made to identify antigens, the humoral response against which leads to protection. Seroepidemiological studies have identified several specific malarial blood-stage antigens including ring-infected erythrocyte surface antigen (10), apical membrane antigen (53), and PfP0, a conserved ribosomal protein (7,18,24), as protective antigens.Enolase has been reported to be present on the cell surface of several organisms (38). It is also considered to be a major immunostimulatory protein in the case of visceral leishmaniasis (19). Enolase has been demonstrated to play a protective role in Candida albicans infection (31, 41, 55). Recently, it has also been ...

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Section: Discussionmentioning

confidence: 93%

Protective Properties and Surface Localization ofPlasmodium falciparumEnolase

et al. 2007

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“…Importantly, recent studies have shown that enolase has functional diversity and is a plasminogenbinding protein in other pathogenic organisms, including Fasciola hepatica (12), Streptococcus spp. (11,39), and Staphylococcus aureus (34).…”

Section: Discussionmentioning

confidence: 99%

Adherence to Human Vaginal Epithelial Cells Signals for Increased Expression of Trichomonas vaginalis Genes

2005

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Host parasitism byTrichomonas vaginalis colonizes the urogenital tract of humans, causing trichomonosis, the number one nonviral sexually transmitted disease worldwide. Despite an estimated 8 million new cases per year in the United States alone (53), this health disparities disease (48) remains poorly studied. T. vaginalis infection is associated with adverse health consequences to both men and women, including infertility (20, 46), atypical pelvic inflammatory disease (35), and increased human immunodeficiency virus transmission (24,49). Trichomonosis is also associated with preterm birth, low-birth-weight infants (16), predisposition to development of cervical neoplasia in women (51), and nongonococcal urethritis (9) and chronic prostatitis (10) in men. The complex interplay of trichomonad responses and that of the host cells during infection have not been investigated so far. Of the few reports concerning host-parasite interactions, one study showed that after short contact of trichomonads with host vaginal epithelial cells (VECs), but not HeLa cells, the parasite morphology is transformed from an ellipsoid to an amoeboid form (8), suggesting host-specific signaling of parasites. In addition, synthesis of all four adhesin proteins in the amoeboid forms bound to VECs was enhanced (8,22). In a separate study using different forms of parasites grown in culture flasks, ␣-actinin was shown to be overexpressed in amoeboid parasites compared to batch-cultured ellipsoid trichomonads (1).The transcriptional regulation of parasite genes in response to interactions with host cells using in vitro models has been studied in Neisseria meningitides (23), Porphyromonas gingivalis (25, 41), and Helicobacter pylori (26). Due to the lack of a good animal model system to study T. vaginalis pathogenesis, we have used an in vitro model of immortalized human VECs (22) in our present study. Because of the unavailability of genome sequence data at the time this study was initiated, we used the subtraction cDNA library approach to identify the transcriptional changes in gene expression during the initial step of T. vaginalis attachment to VECs. Differentially expressed gene profiling using cDNA subtraction has been an ideal tool in identifying novel genes and transcripts of low abundance (13). Our data identify numerous T. vaginalis genes that are upregulated upon contact, which was confirmed by semiquantitative reverse transcription-PCR (RT-PCR) and protein immunoblot analyses. We believe that functional analyses of up-regulated genes of both VECs, as done recently (29), and of the organisms after the adherence event will contribute to our understanding of the host-pathogen interrelationship and the elucidation of the mechanisms of pathogenesis. MATERIALS AND METHODSParasites and host cells. T. vaginalis isolate T016 was grown in trypticase-yeast extract-maltose (TYM) medium supplemented with 10% serum at 37°C (19). For iron-replete parasites, TYM serum was supplemented with 200 M ferrous ammonium sulfate, and iron-depleted parasite...

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“…For example, surface glyceraldehyde-3-phosphate dehydrogenase and ␣-enolase are without signal sequences and membrane-anchoring motifs and are known to be secreted before reassociation with surfaces of prokaryotic and eukaryotic cells (11,12,22,41). These enzymes exhibit ligand-binding, nonenzymatic functions that play important roles in colonization and invasion (10,11,13,22,41).…”

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confidence: 99%

Immunogenic and Plasminogen-Binding Surface-Associated α-Enolase of Trichomonas vaginalis

2008

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Trichomonas vaginalis is a protist that causes the most common human sexually transmitted infection. A T. vaginalis cDNA expression library was screened with pooled sera from patients with trichomoniasis. A highly reactive cDNA clone of 1,428 bp encoded a trichomonad protein of 472 amino acids with sequence identity to ␣-enolase (tv-eno1). The sequence alignment confirmed the highly conserved nature of the enzyme with 65% to 84% identity among organisms. The expression of tv-eno1 was up-regulated by contact of parasites with vaginal epithelial cells, and this is the first report demonstrating up-regulation by cytoadherence of a plasminogenbinding ␣-enolase in T. vaginalis. Immunofluorescence with monoclonal antibody of nonpermeabilized trichomonads showed tv-ENO1 on the surface. The recombinant tv-ENO1 was expressed in Escherichia coli as a glutathione S-transferase (GST)::tv-ENO1 fusion protein, which was cleaved using thrombin to obtain affinity-purified recombinant tv-ENO1 protein (tv-rENO1) detectable in immunoblots by sera of patients. Immobilized tv-rENO1 bound human plasminogen in a dose-dependent manner, and plasminogen binding by tv-rENO1 was confirmed in a ligand blot assay. The plasminogen-specific inhibitor -aminocaproic acid blocked the tv-rENO1-plasminogen association, indicating that lysines play a role in binding to tv-rENO1. Further, both parasites and tv-rENO1 activate plasminogen to plasmin that is mediated by tissue plasminogen activator. These data indicate that as with other bacterial pathogens, tv-ENO1 is an anchorless, surfaceassociated glycolytic enzyme of T. vaginalis.Trichomonas vaginalis is responsible for the number one, nonviral sexually transmitted disease worldwide (56). There are 250 million new cases of trichomoniasis worldwide and ϳ9 million cases in the United States (15,55,57). Trichomoniasis is known to increase the portal of entry and exit for human immunodeficiency virus (51). A recent study showed serological evidence linking trichomoniasis with prostate cancer (52). Given the significant human morbidity caused by T. vaginalis, there is a need for identifying virulence factors and elucidating the mechanisms of disease pathogenesis.A prerequisite for T. vaginalis infection is its ability to colonize the vaginal epithelium. Surface-associated adhesin proteins were shown to be involved in parasite adherence to vaginal epithelial cells (VECs) (4,19,20). There is a direct relationship between the amount of surface adhesin that binds to host cells in a ligand-receptor type interaction (8,20) and the level of cytoadherence (8,20). Contact with VECs produces a dramatic change in morphology accompanied by synthesis of adhesins (9, 26). A recent study using antisense RNA reaffirmed the importance of AP65 and AP33 in parasite associations with VECs (37, 38). In addition, heterologous expression of AP65 and AP33 on the Tritrichomonas foetus surface provided evidence that both are bona fide adhesins of T. vaginalis (25,38). Interestingly, these adhesins show sequence identity to metab...

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Identification of enolase as a plasminogen‐binding protein in excretory–secretory products of Fasciola hepatica

Cited by 129 publications

References 35 publications

Protective Properties and Surface Localization ofPlasmodium falciparumEnolase

Protective Properties and Surface Localization ofPlasmodium falciparumEnolase

Adherence to Human Vaginal Epithelial Cells Signals for Increased Expression of Trichomonas vaginalis Genes

Immunogenic and Plasminogen-Binding Surface-Associated α-Enolase of Trichomonas vaginalis

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