Enzymes on microbial pathogens and Trichomonas vaginalis: molecular mimicry and functional diversity

Genetic Variability of the Internal Transcribed Spacer and Pyruvate:Ferredoxin Oxidoreductase Partial Gene of Trichomonas vaginalis from Female Patients

In the present study, we evaluated the genetic variability of the internal transcribed spacer (ITS) region and the pyruvate:ferredoxin oxidoreductase (pfor) A gene of Trichomonas vaginalis from female patients and its possible implications in the host-parasite relationship. Phylogenetic and genetics of populations analyses were performed by analyzing sequences of the ITS region and partial pfor A gene of clinical samples with T. vaginalis, as previously documented. Alignments of protein sequences and prediction of three-dimensional structure were also performed. Although no correlation between the main clinical characteristics of the samples and the results of phylogeny was found, a median-joining analysis of ITS haplotypes showed two main clusters. Also, pfor A, due to its phylogenetic divergence, could be used as a marker to confirm the genus and species of trichomonads. Alignment of protein sequences and prediction of three-dimensional structure showed that PFOR A had a highly conserved structure with two synonymous mutations in the PFOR domain, substituting a V for a G or a S for a P. Our results suggest that the role of genetic variability of PFOR and ITS may not be significant in the symptomatology of this pathogen; however, their utility as genus and species markers in trichomonads is promising.

Integrated proteomics, genomics, metabolomics approaches reveal oxalic acid as pathogenicity factor in Tilletia indica inciting Karnal bunt disease of wheat

Tilletia indica incites Karnal bunt (KB) disease in wheat. To date, no KB resistant wheat cultivar could be developed due to non-availability of potential biomarkers related to pathogenicity/virulence for screening of resistant wheat genotypes. The present study was carried out to compare the proteomes of T. indica highly (TiK) and low (TiP) virulent isolates. Twenty one protein spots consistently observed as up-regulated/differential in the TiK proteome were selected for identification by MALDI-TOF/TOF. Identified sequences showed homology with fungal proteins playing essential role in plant infection and pathogen survival, including stress response, adhesion, fungal penetration, invasion, colonization, degradation of host cell wall, signal transduction pathway. These results were integrated with T. indica genome sequence for identification of homologs of candidate pathogenicity/virulence related proteins. Protein identified in TiK isolate as malate dehydrogenase that converts malate to oxaloacetate which is precursor of oxalic acid. Oxalic acid is key pathogenicity factor in phytopathogenic fungi. These results were validated by GC-MS based metabolic profiling of T. indica isolates indicating that oxalic acid was exclusively identified in TiK isolate. Thus, integrated omics approaches leads to identification of pathogenicity/virulence factor(s) that would provide insights into pathogenic mechanisms of fungi and aid in devising effective disease management strategies.

Trichomoniasis - are we giving the deserved attention to the most common non-viral sexually transmitted disease worldwide?

ETIOLOGY

Trichomonas vaginalis is the etiologic agent of trichomoniasis, the most common non-viral sexually transmitted disease (STD) in the world. Transmission: Trichomoniasis is transmitted by sexual intercourse and transmission via fomites is rare. Epidemiology, incidence and prevalence: The WHO estimates an incidence of 276 million new cases each year and prevalence of 187 million of infected individuals. However, the infection is not notifiable. Pathology/Symptomatology: The T. vaginalis infection results in a variety of clinical manifestations - in most cases the patients are asymptomatic, but some may develop signs typically associated to the disease. Importantly, the main issue concerning trichomoniasis is its relationship with serious health consequences such as cancer, adverse pregnancy outcomes, infertility, and HIV acquisition. Molecular mechanisms of infection: To achieve success in parasitism trichomonads develop a complex process against the host cells that includes dependent- and independent-contact mechanisms. This multifactorial pathogenesis includes molecules such as soluble factors, secreted proteinases, adhesins, lipophosphoglycan that culminate in cytoadherence and cytotoxicity against the host cells. Treatment and curability: The treatment with metronidazole or tinidazole is recommended; however, cure failures remain problematic due to noncompliance, reinfection and/or lack of treatment of sexual partners, inaccurate diagnosis, or drug resistance. Therefore, new therapeutic alternatives are urgently needed. Protection: Strategies for protection including sexual behavior, condom usage, and therapy have not contributed to the decrease on disease prevalence, pointing to the need for innovative approaches. Vaccine development has been hampered by the lack of long-lasting humoral immunity associated to the absence of good animal models.

Mechanisms of Tritrichomonas foetus Pathogenicity in Cats with Insights from Venereal Trichomonosis

Almost 20 years has passed since trichomonosis was first recognized as a potential cause of diarrhea in domestic cats. Despite progress in confirming disease causation, developing means for diagnosis, and identifying approaches to treatment of the infection, we still know very little about how this parasite causes diarrhea. With increasing recognition of resistance of trichomonosis to treatment with 5‐nitroimidazole drugs, new treatment strategies based on an understanding of disease pathogenesis are needed. In this review, lessons learned from the pathogenesis of venereal trichomonosis in people and cattle are applied to clinical observations of trichomonosis in cats in effort to generate insight into areas where further research may be beneficial.

The adherence of Trichomonas vaginalis to host ectocervical cells is influenced by lactobacilli

OBJECTIVES

Trichomoniasis is a common sexually transmitted disease, and adhesion of the pathogen Trichomonas vaginalis to the host vaginal cells is the first step in establishing infection. For this to happen, the pathogen has to overcome a natural protective barrier composed mostly of lactobacilli. The objective of this study was to understand the role of lactobacilli in the adhesion of T vaginalis to host cells.

METHODS

Adhesion assays were carried out by incubating vaginal epithelial cells (VECs) with T vaginalis and lactobacilli together and compared with non-lactobacilli recipient controls. By varying incubation parameters and testing several microbial isolates, the number of pathogens that adhered to the VECs was determined by flow cytometry.

RESULTS

Overall, but with few exceptions, lactobacilli caused inhibition of T vaginalis adhesion to a variable degree. Lactobacillus gasseri ATCC 9857 and CBI3 (ambiguous Lactobacillus plantarum or Lactobacillus pentosus) caused the highest level of parasite adhesion inhibition and enhancement, respectively. These isolates of Lactobacillus can profoundly alter the adhesive properties of low-adherent and high-adherent strains of T vaginalis in a dose-dependent manner. Additionally, the effects of lactobacilli on T vaginalis adhesion are strictly contact-dependent, and surface lipoglycans of T vaginalis are most likely not involved in this modulation of adhesion mediated by the bacteria.

CONCLUSIONS

Lactobacilli can modulate adhesion of T vaginalis by significantly modifying the natural adhesive properties of various T vaginalis strains. This study highlights the importance of considering the role of the vaginal microbiota in the pathogenesis of trichomoniasis.

Iron-inducible nuclear translocation of a Myb3 transcription factor in the protozoan parasite Trichomonas vaginalis

In Trichomonas vaginalis, a novel nuclear localization signal spanning the folded R2R3 DNA-binding domain of a Myb2 protein was previously identified. To study whether a similar signal is used for nuclear translocation by other Myb proteins, nuclear translocation of Myb3 was examined in this report. When overexpressed, hemagglutinin-tagged Myb3 was localized to nuclei of transfected cells, with a cellular distribution similar to that of endogenous Myb3. Fusion to a bacterial tetracycline repressor, R2R3, of Myb3 that spans amino acids (aa) 48 to 156 was insufficient for nuclear translocation of the fusion protein, unless its C terminus was extended to aa 167. The conserved isoleucine in helix 2 of R2R3, which is important for Myb2's structural integrity in maintaining DNA-binding activity and nuclear translocation, was also vital for the former activity of Myb3, but less crucial for the latter. Sequential nuclear influx and efflux of Myb3, which require further extension of the nuclear localization signal to aa 180, were immediately induced after iron repletion. Sequence elements that regulate nuclear translocation with cytoplasmic retention, nuclear influx, and nuclear efflux were identified within the C-terminal tail. These results suggest that the R2R3 DNA-binding domain also serves as a common module for the nuclear translocation of both Myb2 and Myb3, but there are intrinsic differences between the two nuclear localization signals.

Trichomonas vaginalis: current understanding of host-parasite interactions

Trichomonas vaginalis is a sexually transmitted obligate extracellular parasite that colonizes the human urogenital tract. Despite being of critical importance to the parasite's survival relatively little is known about the mechanisms employed by T. vaginalis to establish an infection and thrive within its host. Several studies have focused on the interaction of the parasite with host cells and extracellular matrix, identifying multiple suspected T. vaginalis adhesins. However, with the exception of its surface lipophosphoglycan, the evidence supporting a role in adhesion is indirect or controversial for many candidate molecules. The availability of the T. vaginalis genome sequence paved the way for genomic analyses to search for proteins possibly involved in host-parasite interactions. Several proteomic analyses have also provided insight into surface, soluble and secreted proteins that may be involved in Trichomonas pathogenesis. Although the accumulation of molecular data allows for a more rational approach towards identifying drug targets and vaccine candidates for this medically important parasite, a continued effort is required to advance our understanding of its biology. In the present chapter, we review the current status of research aimed at understanding T. vaginalis pathogenesis. Applied experimental approaches, an overview of significant conclusions drawn from this research and future challenges are discussed.

Involvement of purinergic signaling on nitric oxide production by neutrophils stimulated with Trichomonas vaginalis

Trichomonas vaginalis is a parasite from the human urogenital tract that causes trichomonosis, the most prevalent non-viral sexually transmitted disease. The neutrophil infiltration has been considered to be primarily responsible for cytological changes observed at infection site, and the chemoattractants can play an important role in this leukocytic recruitment. Nitric oxide (NO) is one of the most widespread mediator compounds, and it is implicated in modulation of immunological mechanisms. Extracellular nucleotides and nucleosides are signaling molecules involved in several processes, including immune responses and control of leukocyte trafficking. Ectonucleoside triphosphate diphosphohydrolase members, ecto-5'-nucleotidase, and adenosine deaminase (ectoADA) have been characterized in T. vaginalis. Herein, we investigated the effects of purinergic system on NO production by neutrophils stimulated with T. vaginalis. The trophozoites were able to induce a high NO synthesis by neutrophils through iNOS pathway. The extracellular nucleotides ATP, ADP, and ATPγS (a non-hydrolyzable ATP analog) showed no significant change in NO secretion. In contrast, adenosine and its degradation product, inosine, promoted a low production of the compound. The immunosuppressive effect of adenosine upon NO release by neutrophils occurred due to adenosine A(2A) receptor activation. The ecto-5'-nucleotidase activity displayed by T. vaginalis was shown to be important in adenosine generation, indicating the efficiency of purinergic cascade. Our data suggest the influence of purinergic signaling, specifically adenosinergic system, on NO production by neutrophils in T. vaginalis infection, contributing to the immunological aspects of disease.

Pyruvate : ferredoxin oxidoreductase (PFO) is a surface-associated cell-binding protein in Trichomonas vaginalis and is involved in trichomonal adherence to host cells

The Trichomonas vaginalis 120 kDa protein adhesin (AP120) is induced under iron-rich conditions and has sequence homology with pyruvate : ferredoxin oxidoreductase A (PFO A), a hydrogenosomal enzyme that is absent in humans. This homology raises the possibility that, like AP120, PFO might be localized to the parasite surface and participate in cytoadherence. Here, the cellular localization and function of PFO that was expressed under various iron concentrations was investigated using a polyclonal antibody generated against the 50 kDa recombinant C-terminal region of PFO A (anti-PFO50). In Western blot assays, this antibody recognized a 120 kDa protein band in total protein extracts, and proteins with affinity to the surface of HeLa cells from parasites grown under iron-rich conditions. In addition to localization that is typical of hydrogenosomal proteins, PFOs that were expressed under iron-rich conditions were found to localize at the surface. This localization was demonstrated using immunofluorescence and co-localization assays, as well as immunogold transmission electron microscopy. In addition to describing its enzyme activity, we describe a novel function in trichomonal host interaction for the PFO localized on the parasite surface. The anti-PFO50 antibody reduced the levels of T. vaginalis adherence to HeLa cell monolayers in a concentration-dependent manner. Thus, T. vaginalis PFO is an example of a surface-associated cell-binding protein that lacks enzyme activity and that is involved in cytoadherence. Additionally, PFO behaves like AP120 in parasites grown under iron-rich conditions. Therefore, these data suggest that AP120 and PFO A are encoded by the same gene, namely pfo a.

Chemical structure of Trichomonas vaginalis surface lipoglycan: a role for short galactose (β1-4/3) N-acetylglucosamine repeats in host cell interaction

The extracellular parasite Trichomonas vaginalis contains a surface glycoconjugate that appears to mediate parasite-host cell interaction via binding to human galectin-1. This glycoconjugate also elicits cytokine production from human vaginal epithelial cells, implicating its role in modulation of host immune responses. We have analyzed the structure of this glycoconjugate, previously described to contain the sugars rhamnose (Rha), N-acetylglucosamine (GlcNAc), galactose (Gal), xylose (Xyl), N-acetylgalactosamine (GalNAc), and glucose (Glc), using gas chromatograph mass spectrometry (GC-MS), matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF), electrospray MS/MS, and nuclear magnetic resonance (NMR), combined with chemical and enzymatic digestions. Our data reveal a complex structure, named T. vaginalis lipoglycan (TvLG), that differs markedly from Leishmania lipophosphoglycan and Entamoeba lipopeptidophosphoglycan and is devoid of phosphosaccharide repeats. TvLG is composed of an α1–3 linked polyrhamnose core, where Rha residues are substituted at the 2-position with either β-Xyl or chains of, on average, five N-acetyllactosamine (-3Galβ1–4GlcNAcβ1-) (LacNAc) units and occasionally lacto-N-biose (-3Galβ1-3GlcNAcβ1-) (LNB). These chains are themselves periodically substituted at the Gal residues with Xyl-Rha. These structural analyses led us to test the role of the poly-LacNAc/LNB chains in parasite binding to host cells. We found that reduction of poly-LacNAc/LNB chains decreased the ability of TvLG to compete parasite binding to host cells. In summary, our data provide a new model for the structure of TvLG, composed of a polyrhamnose backbone with branches of Xyl and poly-LacNAc/LNB. Furthermore, the poly-LacNAc side chains are shown to be involved in parasite-host cell interaction.

Proteomic changes associated with deletion of the Magnaporthe oryzae conidial morphology-regulating gene COM1

BACKGROUND

The rice blast disease caused by Magnaporthe oryzae is a major constraint on world rice production. The conidia produced by this fungal pathogen are the main source of disease dissemination. The morphology of conidia may be a critical factor in the spore dispersal and virulence of M. oryzae in the field. Deletion of a conidial morphology regulating gene encoding putative transcriptional regulator COM1 in M. oryzae resulted in aberrant conidial shape, reduced conidiation and attenuated virulence.

RESULTS

In this study, a two-dimensional gel electrophoresis/matrix assisted laser desorption ionization- time of flight mass spectrometry (2-DE/MALDI-TOF MS) based proteomics approach was employed to identify the cellular and molecular components regulated by the COM1 protein (COM1p) that might contribute to the aberrant phenotypes in M. oryzae. By comparing the conidial proteomes of COM1 deletion mutant and its isogenic wild-type strain P131, we identified a potpourri of 31 proteins that exhibited statistically significant alterations in their abundance levels. Of these differentially regulated proteins, the abundance levels of nine proteins were elevated and twelve were reduced in the Δcom1 mutant. Three proteins were detected only in the Δcom1 conidial proteome, whereas seven proteins were apparently undetectable. The data obtained in the study suggest that the COM1p plays a key role in transcriptional reprogramming of genes implicated in melanin biosynthesis, carbon and energy metabolism, structural organization of cell, lipid metabolism, amino acid metabolism, etc. Semi-quantitative RT-PCR analysis revealed the down-regulation of genes encoding enzymes involved in melanin biosynthesis in the COM1 mutant.

CONCLUSIONS

Our results suggest that the COM1p may regulate the transcription of genes involved in various cellular processes indispensable for conidial development and appressorial penetration. These functions are likely to contribute to the effects of COM1p upon the aberrant phenotypes of M. oryzae.

Proteomic assessment of host-associated microevolution in the fungus Thielaviopsis basicola

Thielaviopsis basicola, a soil-borne pathogen with a broad host range and a cosmopolitan distribution, is emerging as a major risk to sustainable cotton production in Australia. Previous studies suggested that host specialization has occurred making T. basicola an ideal model for a comparative proteomic analysis of strains isolated from different hosts. Elucidation of the genomic diversity and investigation of the functional differences in the Australian population could provide valuable information towards disease control. In this study, isolates of T. basicola were investigated for genomic (internal transcribed spacers region), proteomic and cotton virulence level variations. Internal transcribed spacers sequence analysis revealed that isolates are grouped based on host of origin irrespective of geographical origin. At the proteome level a degree of diversity was apparent and hierarchical clustering analysis of the data also demonstrated a close correlation between the proteome and the host of origin. LC-MS/MS analysis and identification using cross-species similarity searching and de novo sequencing of host-specific differentially expressed proteins and the virulence-correlated proteome allowed successful identification of 43 spots. The majority were found to be involved in metabolism. Spots that were correlated with host and virulence differences included a hypothetical protein with a Rossman-fold NAD(P)(+)-binding protein domain, glyceraldehyde-3-phosphate dehydrogenase, arginase and tetrahydroxynaphthalene reductase.

Cytoplasmic- and extracellular-proteome analysis of Diplodia seriata: a phytopathogenic fungus involved in grapevine decline

BACKGROUND

The phytopathogenic fungus Diplodia seriata, whose genome remains unsequenced, produces severe infections in fruit trees (fruit blight) and grapevines. In this crop is recognized as one of the most prominent pathogens involved in grapevine trunk disease (or grapevine decline). This pathology can result in the death of adult plants and therefore it produces severe economical losses all around the world. To date no genes or proteins have been characterized in D. seriata that are involved in the pathogenicity process. In an effort to help identify potential gene products associated with pathogenicity and to gain a better understanding of the biology of D. seriata, we initiated a proteome-level study of the fungal mycelia and secretome.

RESULTS

Intracellular and secreted proteins from D. seriata collected from liquid cultures were separated using two-dimensional gel electrophoresis. About 550 cytoplasmic proteins were reproducibly present in 3 independent extractions, being 53 identified by peptide mass fingerprinting and tandem mass spectrometry. The secretome analysis showed 75 secreted proteins reproducibly present in 3 biological replicates, being 16 identified. Several of the proteins had been previously identified as virulence factors in other fungal strains, although their contribution to pathogenicity in D. seriata remained to be analyzed. When D. seriata was grown in a medium supplemented with carboxymethylcellulose, 3 proteins were up-regulated and 30 down-regulated. Within the up-regulated proteins, two were identified as alcohol dehydrogenase and mitochondrial peroxyrredoxin-1, suggesting that they could play a significant role in the pathogenicity process. As for the 30 down-regulated proteins, 9 were identified being several of them involved in carbohydrate metabolism.

CONCLUSIONS

This study is the first report on proteomics on D. seriata. The proteomic data obtained will be important to understand the pathogenicity process. In fact, several of the identified proteins have been reported as pathogenicity factors in other phytopathogenic fungi. Moreover, this proteomic analysis supposes a useful basis for deepening into D. seriata knowledge and will contribute to the development of the molecular biology of this fungal strain as it has been demonstrated by cloning the gene Prx1 encoding mitochondrial peroxiredoxin-1 of D. seriata (the first gene to be cloned in this microorganism; data not shown).

Moonlighting enzymes in parasitic protozoa

Enzymes moonlight in a non-enzymatic capacity in a diverse variety of cellular processes. The discovery of these non-enzymatic functions is generally unexpected, and moonlighting enzymes are known in both prokaryotes and eukaryotes. Importantly, this unexpected multi-functionality indicates that caution might be needed on some occasions in interpreting phenotypes that result from the deletion or gene-silencing of some enzymes, including some of the best known enzymes from classic intermediary metabolism. Here, we provide an overview of enzyme moonlighting in parasitic protists. Unequivocal and putative examples of moonlighting are discussed, together with the possibility that the unusual biological characteristics of some parasites either limit opportunities for moonlighting to arise or perhaps contribute to the evolution of novel proteins with clear metabolic ancestry.

Hydrogenosomes under microscopy

A hydrogenosome is a hydrogen-producing organelle, evolutionary related to mitochondria and is found in Parabasalia protozoa, certain chytrid fungi and certain ciliates. It displays similarities to and differences from mitochondria. Hydrogenosomes are spherical or slightly elongated organelles, although very elongated hydrogenosomes are also found. They measure from 200 nm to 1 microm, but under stress conditions can reach up to 2 microm. Hydrogenosomes are surrounded by two closely apposed membranes and present a granular matrix. Cardiolipin has been detected in their membranes, and frataxin, which is a conserved mitochondrial protein involved in iron metabolism, was also recently found. Hydrogenosomes have one or multiple peripheral vesicles, which incorporate calcium. The peripheral vesicle can be isolated from the hydrogenosomal matrix and can be considered as a distinct hydrogenosomal compartment. Dysfunctional hydrogenosomes can be removed by an autophagic process and further digested by lysosomes. Hydrogenosomes divide in three different ways, like mitochondria, by segmentation, partition and the heart form. They may divide at any phase of the cell cycle. Nucleoid or electron dense deposits found in hydrogenosomes can be considered artifacts or dysfunctional hydrogenosomes. The hydrogenosome does not contain a genome, although DNA has already been detected in one anaerobic ciliate. Hydrogenosomes can be considered as good drug targets since their metabolism is distinct from mitochondria.

Proteomic analysis of fungal host factors differentially expressed by Fusarium graminearum infected with Fusarium graminearum virus-DK21

Fusarium graminearum virus-DK21 (FgV-DK21), which infects the plant pathogenic F. graminearum, perturbs host developmental processes such as sporulation, morphology, pigmentation, and attenuates the virulence (hypovirulence) of the host. To identify the differentially expressed F. graminearum proteins by FgV-DK21 infection, we have used two-dimensional electrophoresis with mass spectrometry using proteins extracted from virus-free and FgV-DK21-infected strains. A total of 148 spots showing an altered expression were identified by PDQuest program. Among these spots, 33 spots were exclusively analyzed including 14 spots from FgV-DK21-infected and 19 spots from virus-free strains by ESI-MS/MS analyses and successfully identified 23 proteins. Seven proteins including sporulation-specific gene SPS2, triose phosphate isomerase, nucleoside diphosphate kinase, and woronin body major protein precursor were induced or significantly up-regulated by FgV-DK21 infection. A significant decrease or down regulation of 16 proteins including enolase, saccharopine dehydrogenase, flavohemoglobin, mannitol dehydrogenase and malate dehydrogenase caused by FgV-DK21 infection was also identified. Variations of protein expression were also further investigated at the mRNA level by real-time RT-PCR analysis, which confirmed the proteomic data for 9 out of the representative 11 selected proteins including 5 proteins from up-regulated group and 6 proteins from down-regulated group. Further investigation of these differentially expressed proteins will provide novel insights into the molecular responses of F. graminearum to FgV-DK21 infection.

Identification and molecular characterization of numerous Histomonas meleagridis proteins using a cDNA library

SUMMARYHistomonas meleagridis is a protozoan parasite of various galliform birds causing a type of enterohepatitis termed histomonosis or 'blackhead disease'. Due to the ban of chemotherapeutic substances and an increase in free-range poultry production, histomonosis is currently a re-emerging disease. So far limited molecular knowledge is available. In the present work, mRNAs coding for antigenic proteins of H. meleagridis were identified. For this purpose, a cDNA expression library was constructed from a mono-eukaryotic culture of H. meleagridis. The library was screened with polyclonal rabbit serum raised against purified H. meleagridis trophozoites. Polyclonal rabbit serum specifically recognized the same major H. meleagridis antigens as chicken and turkey sera originating from animal trials, but displayed a significantly lower bacteria-dependent background signal. After 2 rounds of screening, a total of 95 positive clones were sequenced. Bioinformatics analyses were performed on nucleotide and deduced amino acid sequences, identifying 37 unique clones. Based on the homology to other protozoan parasites, mostly Trichomonas vaginalis, the clones were grouped according to functional aspects: structural proteins, possible surface proteins, oxygen reducing proteins, ribosomal proteins, protein kinases and various other intracellular proteins.

The proteins secreted by Trichomonas vaginalis and vaginal epithelial cell response to secreted and episomally expressed AP65

We showed recently that contact of human vaginal epithelial cells (VECs) by Trichomonas vaginalis and incubation with trichomonad proteins in conditioned medium induced expression of VEC genes. We performed 2-D SDS-PAGE followed by MALDI-TOF to identify the major secreted proteins. Based on protein abundance and separation of spots in 2-D gels, 32 major secreted proteins were examined, which gave 19 proteins with accession numbers. These proteins included known secreted cysteine proteinases. In addition, other secreted proteins were enzymes of carbohydrate metabolism, adhesin protein AP65, heat shock proteins, thioredoxin reductase and coronins. We confirmed that the secreted trichomonad proteins induced expression of VEC genes, including interleukin 8 (IL-8), COX-2 and fibronectin. Purified AP65 added to VECs had a pronounced effect only on IL-8 gene expression, which was inhibited in the presence of 12G4 monoclonal antibody to AP65. Moreover, AP65 expressed episomally within epithelial cells was found to enhance the expression of IL-8 and COX-2. This may be the first report of analysis of the secreted proteins of T. vaginalis and of the host epithelial cell response to these proteins and to the prominent adhesin AP65.

Activation of Multifarious Transcription of an Adhesion Protein ap65-1 Gene by a Novel Myb2 Protein in the Protozoan Parasite Trichomonas vaginalis

Multifarious transcription of the adhesion protein ap65-1 gene in the human pathogen, Trichomonas vaginalis, is critically regulated by the coordination of two similar but opposite oriented DNA regulatory regions, MRE-1/MRE-2r and MRE-2f, both of which are binding sites for multiple Myb-like proteins. In the present study, MRE-1/MRE-2r was demonstrated to be composed of multiple overlapping promoter elements, among which the entire region is required for growth-related ap65-1 transcription, and the 5'-MRE-1 antagonizes the suppressive activity of the 3'-MRE-2r in iron-inducible transcription. The recombinant Myb2 protein derived from a previously identified myb2 gene was demonstrated to recognize distinct sequence contexts in MRE-2r and MRE-2f, whereas Myb2 in the nuclear lysate preferentially binds to MRE-2f to MRE-2r. Iron repletion resulted in persistent repression of the myb2 gene, and temporal activation/deactivation of Myb2 promoter entry, which was also activated by prolonged iron depletion. The hemagglutinintagged Myb2 when overexpressed during iron-depleted conditions facilitated basal and growth-related ap65-1 transcription to a level that was achieved in iron-replete cells, whereas ironinducible ap65-1 transcription was abolished with knockdown of Myb2. These findings demonstrated that Myb2 is involved in activation of growth-related and iron-inducible transcription of the ap65-1 gene, possibly through differential promoter selection in competition with other Myb proteins.

Proteomic analysis of phytopathogenic fungus Botrytis cinerea as a potential tool for identifying pathogenicity factors, therapeutic targets and for basic research

Botrytis cinerea is a phytopathogenic fungus causing disease in a substantial number of economically important crops. In an attempt to identify putative fungal virulence factors, the two-dimensional gel electrophoresis (2-DE) protein profile from two B. cinerea strains differing in virulence and toxin production were compared. Protein extracts from fungal mycelium obtained by tissue homogenization were analyzed. The mycelial 2-DE protein profile revealed the existence of qualitative and quantitative differences between the analyzed strains. The lack of genomic data from B. cinerea required the use of peptide fragmentation data from MALDI-TOF/TOF and ESI ion trap for protein identification, resulting in the identification of 27 protein spots. A significant number of spots were identified as malate dehydrogenase (MDH) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The different expression patterns revealed by some of the identified proteins could be ascribed to differences in virulence between strains. Our results indicate that proteomic analysis are becoming an important tool to be used as a starting point for identifying new pathogenicity factors, therapeutic targets and for basic research on this plant pathogen in the postgenomic era.

Two-dimensional electrophoresis protein profile of the phytopathogenic fungus Botrytis cinerea

Botrytis cinerea is a phytopathogenic fungi causing disease in a number of important crops. It is considered a very complex species in which different populations seem to be adapted to different hosts. In order to characterize fungal virulence factors, a proteomic research was started. A protocol for protein extraction from mycelium tissue, with protein separation by 2-DE and MS analysis, was optimised as a first approach to defining the B. cinerea proteome. Around 400 spots were detected in 2-DE CBB-stained gels, covering the 5.4-7.7 pH and 14-85 kDa ranges. The averages of analytical and biological coefficients of variance for 64 independent spots were 16.1% and 37.5%, respectively. Twenty-two protein spots were identified by MALDI-TOF or ESI IT MS/MS, with some of them corresponding to forms of malate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase. Two more spots matched a cyclophilin and a protein with an unknown function.

A Trichomonas vaginalis 120 kDa protein with identity to hydrogenosome pyruvate:ferredoxin oxidoreductase is a surface adhesin induced by iron

Trichomonas vaginalis, a human sexually transmitted protozoan, relies on adherence to the vaginal epithelium for colonization and maintenance of infection in the host. Thus, adherence molecules play a fundamental role in the trichomonal infection. Here, we show the identification and characterization of a 120 kDa surface glycoprotein (AP120) induced by iron, which participates in cytoadherence. AP120 is synthesized by the parasite when grown in 250 microM iron medium. Antibodies to AP120 and the electro-eluted AP120 inhibited parasite adherence in a concentration-dependent manner, demonstrating its participation in cytoadherence. In addition, a protein of 130 kDa was detected on the surface of HeLa cells as the putative receptor for AP120. By peptide matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), the AP120 adhesin showed homology with a hydrogenosomal enzyme, the pyruvate:ferredoxin oxidoreductase (PFO) encoded by the pfoa gene. This homology was confirmed by immunoblot and indirect immunofluorescence assays with an antibody to the carboxy-terminus region of the Entamoeba histolytica PFO. Reverse transcription polymerase chain reaction (RT-PCR) assays showed that a pfoa-like gene was better transcribed in trichomonads grown in iron-rich medium. In conclusion, the homology of AP120 to PFO suggests that this novel adhesin induced by iron could be an example of moonlighting protein in T. vaginalis.

Trichomonas vaginalis polyamine metabolism is linked to host cell adherence and cytotoxicity

Trichomonas vaginalis secretes putrescine that is readily detected in vaginal secretions. We wanted to examine the effect of decreased putrescine synthesis by inhibition of ornithine decarboxylase (ODC) on T. vaginalis. One reason is because inhibition of Tritrichomonas foetus ODC results in growth arrest, destruction of hydrogenosomes, and decreased amounts of hydrogenosomal enzymes. Treatment of T. vaginalis T016 with >/=20 mM 1,4-diamino-2-butanone (DAB) to inhibit ODC resulted in growth arrest, which was reversed by addition of exogenous putrescine. No similar reversal of growth arrest was achieved with the polyamines spermine or spermidine or with iron. Electron microscopic examination of control versus DAB-treated trichomonads did not reveal any adverse effects on the number and integrity of hydrogenosomes. Further, the adhesins AP65, AP51, and AP33 mediating binding to immortalized vaginal epithelial cells (VECs) share identity to enzymes of the hydrogenosome organelle, and there was no difference in amounts of adhesins between control versus DAB-treated T. vaginalis parasites. Likewise, similar patterns and extent of fluorescence were evident for the prominent AP65 adhesin. Surprisingly, DAB treatment increased by 4- to 20-fold above untreated trichomonads handled identically the level of adherence mediated by adhesins. Interestingly, the enhanced attachment to VECs was reversed by exogenous putrescine added to DAB-treated trichomonads. Equally noteworthy was that DAB-treated T. vaginalis with enhanced adherence did not possess the previously reported ability to kill host cells in a contact-dependent fashion mediated by cysteine proteinases, and total cysteine proteinase activity patterns were identical between control and DAB-treated trichomonads. Overall, these data suggest that polyamine metabolism and secreted putrescine are linked to host cell adherence and cytotoxicity.

Glyceraldehyde-3-phosphate dehydrogenase, apoptosis, and neurodegenerative diseases

Increasing evidence supports the notion that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a protein with multiple functions, including its surprising role in apoptosis. GAPDH is overexpressed and accumulates in the nucleus during apoptosis induced by a variety of insults in diverse cell types. Knockdown of GAPDH using an antisense strategy demonstrates its involvement in the apoptotic cascade in which GAPDH nuclear translocation appears essential. Knowledge concerning the mechanisms underlying GAPDH nuclear translocation and subsequent cell death is growing. Additional evidence suggests that GAPDH may be an intracellular sensor of oxidative stress during early apoptosis. Abnormal expression, nuclear accumulation, changes in physical properties, and loss of glycolytic activity of GAPDH have been found in cellular and transgenic models as well as postmortem tissues of several neurodegenerative diseases. The interaction of GAPDH with disease-related proteins as well as drugs used to treat these diseases suggests that it is a potential molecular target for drug development.

Heterologous expression in Tritrichomonas foetus of functional Trichomonas vaginalis AP65 adhesin

Background

Trichomonosis, caused by Trichomonas vaginalis, is the number one, nonviral sexually transmitted infection that has adverse consequences for the health of women and children. The interaction of T. vaginalis with vaginal epithelial cells (VECs), a step preparatory to infection, is mediated in part by the prominent surface protein AP65. The bovine trichomonad, Tritrichomonas foetus, adheres poorly to human VECs. Thus, we established a transfection system for heterologous expression of the T. vaginalis AP65 in T. foetus, as an alternative approach to confirm adhesin function for this virulence factor.

Results

In this study, we show stable transfection and expression of the T. vaginalis ap65 gene in T. foetus from an episomal pBS-ap65-neo plasmid. Expression of the gene and protein was confirmed by RT-PCR and immunoblots, respectively. AP65 in transformed T. foetus bound to host cells. Specific mAbs revealed episomally-expressed AP65 targeted to the parasite surface and hydrogenosome organelles. Importantly, surface-expression of AP65 in T. foetus paralleled increased levels of adherence of transfected bovine trichomonads to human VECs.

Conclusion

The T. vaginalis AP65 adhesin was stably expressed in T. foetus, and the data obtained using this heterologous system strongly supports the role of AP65 as a prominent adhesin for T. vaginalis. In addition, the heterologous expression in T. foetus of a T. vaginalis gene offers an important, new approach for confirming and characterizing virulence factors.

Silencing the ap65 gene reduces adherence to vaginal epithelial cells by Trichomonas vaginalis

Host parasitism by Trichomonas vaginalis is complex and in part mediated by adherence to vaginal epithelial cells (VECs). Four trichomonad surface proteins bind VECs as adhesins, and AP65 is a major adhesin with sequence identity to an enzyme of the hydrogenosome organelle that is involved in energy generation. In order to perform genetic analysis and assess the role of AP65 in T. vaginalis adherence, we silenced expression of ap65 using antisense RNA. The gene for ap65 was inserted into the vector pBS-neo in sense and antisense orientations to generate plasmids pBS-neoS (S) and pBS-neoAS (AS), respectively. Trichomonads were then transfected with S and AS plasmids for selection of stable transfectants using Geneticin, and the presence of plasmid in transfectants was confirmed by polymerase chain reaction of the neo gene. Reverse transcription polymerase chain reaction and Northern blot analysis showed decreased amounts of ap65 transcript in AS transfected parasites. Growth kinetics of the antisense-transfected and wild type organisms were similar, suggesting that silencing AP65 did not affect overall energy generation for growth. Immunoblot analysis using monoclonal antibody (mAb) to AP65 of AS transfectants showed decreased amounts of AP65 when compared to wild type or S transfectants. Not unexpectedly, this corresponded to decreased amounts of AP65 bound to VECs in a functional ligand assay. Reduction in parasite surface expression of AP65 was related to lower levels of adherence to VECs by AS-transfectants compared to control organisms. Antisense silencing of ap65 was not alleviated by growth of trichomonads in high iron, which up-regulates transcription of ap65. Our work reaffirms the role for AP65 as an adhesin, and in addition, we demonstrate antisense RNA gene silencing in T. vaginalis to study the contribution of specific genes in pathogenesis.

Involvement of multiple DNA elements in iron-inducible transcription of the ap65-1 gene in the protozoan parasite Trichomonas vaginalis

A reputed iron-responsive region, which contains multiple nuclear protein-binding DNA sequences, was shown previously to regulate iron-inducible transcription of the ap65-1 gene in the protozoan pathogen, Trichomonas vaginalis. These DNA sequences include two overlapping MYB recognition elements (MRE-1/MRE-2r) and three abutted T-tract elements. Additional nuclear protein-binding DNA sequences flanking the 5' (AGTGAAGTGA) and 3' (MRE-2f) of the iron-responsive region were identified in the present study. A stable promoter assay and primer extension revealed that transcriptional activity of the ap65-1 promoter is iron inducible as well as growth related, being lowest in the early logarithmic phase and highest in the mid-logarithmic phase. Subsequent mutational analysis of individual DNA elements of the ap65-1 promoter suggests that closely spaced T-tract elements together with an intervening GAAGGAAG sequence within the iron-responsive region are most critical for regulation of overall transcriptional activity, whereas an additional AGTGAAGTGA and MRE-2f together with an upstream T-rich region are required for optimal iron-inducible activity, and the MRE-1/MRE-2r overlap is only involved in growth-related activity. These observations suggest that expression of the ap65-1 gene is dynamically regulated under various growth conditions via interactions among multiple DNA regulatory elements.

Subcellular localization of human glyceraldehyde-3-phosphate dehydrogenase is independent of its glycolytic function

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was considered a classical glycolytic protein involved exclusively in cytosolic energy production. However, recent evidence suggests that it is a multifunctional protein displaying diverse activities distinct from its conventional metabolic role. These new roles for GAPDH may be dependent on its subcellular localization, oligomeric state or on the proliferative state of the cell. GAPDH is encoded by a single gene without alternate splicing. The regulatory mechanisms are unknown through which an individual GAPDH molecule fulfills its non-glycolytic functions or is targeted to a specific intracellular localization. Accordingly, as a first step to elucidate these subcellular regulatory mechanisms, we examined the interrelationship between the intracellular expression of the GAPDH protein and its glycolytic function in normal human fetal and senior cells. GAPDH localization was determined by immunoblot analysis. Enzyme activity was quantitated by in vitro biochemical assay. We now report that the subcellular expression of GAPDH was independent of its classical glycolytic function. In particular, in both fetal and senior cells, considerable GADPH protein was present in intracellular domains characterized by significantly reduced catalysis. Gradient analysis indicated that this lower activity was not due to the dissociation of tetrameric GAPDH. These results suggest that human cells contain significant intracellular levels of enzymatically inactive GAPDH which is age-independent. The possibility is considered that the functional diversity of GAPDH may be mediated either by posttranslational alteration or by subcellular protein:protein and/or protein:nucleic acid interactions.

Iron and contact with host cells induce expression of adhesins on surface of Trichomonas vaginalis

The proteins AP65, AP51, AP33 and AP23 synthesized by Trichomonas vaginalis organisms in high iron play a role in adherence. Multigene families encode enzymes of the hydrogenosome organelles, which have identity to adhesins. This fact raises questions regarding the compartmentalization of the proteins outside the organelle and about the interactions of adhesins with host cells. Data here demonstrate the presence of the proteins outside the organelle under high-iron conditions. Fluorescence and immuno-cytochemical experiments show that high-iron-grown organisms coexpressed adhesins on the surface and intracellularly in contrast with low-iron parasites. Furthermore, the AP65 epitopes seen by rabbit anti-AP65 serum that blocks adherence and detects surface proteins were identified, and a mAb reacting to those epitopes recognized the trichomonal surface. Two-dimensional electrophoresis and immunoblot of adhesins from surface-labelled parasites provided evidence that all members of the multigene family were co-ordinately expressed and placed on the trichomonal surface. Similar two-dimensional analysis of proteins from purified hydrogenosomes obtained from iodinated trichomonads confirmed the specific surface labelling of proteins. Contact of trichomonads with vaginal epithelial cells increased the amount of surface-expressed adhesins. Moreover, we found a direct relationship between the levels of adherence and amount of adhesins bound to immortalized vaginal and ureter epithelial cells, further reinforcing specific associations. Finally, trichomonads of MR100, a drug-resistant isolate absent in hydrogenosome proteins and adhesins, were non-adherent. Overall, the results confirm an important role for iron and contact in the surface expression of adhesins of T. vaginalis organisms.

Housekeeping enzymes as virulence factors for pathogens

Housekeeping enzymes are ubiquitously present in almost all living beings to perform essential metabolic functions for the purpose of survival. These enzymes have been characterized in detail for many years. In recent years, there has been a number of reports indicating that some of these enzymes perform a variety of other functions. In case of many pathogens, certain enzymes play a role to enhance virulence. To perform such a function, enzymes must be located on the surface of pathogens. Although they do not have the typical signal sequence or membrane anchoring mechanisms, they do get secreted and are displayed on the surface, probably by their reassociation. Once on the surface, these enzymes interact with host components, such as fibronectin and plasminogen, or interact directly with the host cells, to trigger signal transduction and thereby enable the pathogens to colonize, persist and invade the host tissue. Therefore, certain housekeeping enzymes may act as putative virulence factors and targets for the development of new strategies to control the infection by using agents that can block their secretion and/or reassociation.

Trichomonas vaginalis: evaluating capsid proteins of dsRNA viruses and the dsRNA virus within patients attending a sexually transmitted disease clinic

Some isolates of Trichomonas vaginalis, the number one, non-viral sexually transmitted disease agent, are infected with one or several distinct double stranded (ds)-RNA virus. Immune rabbit anti-capsid serum (IRS) reacted with the capsid protein of purified dsRNA virus of a subset of the virus-infected T. vaginalis isolates. A monoclonal antibody (mAb) that recognized the capsid protein reactive with the IRS was generated. Analysis of the virus capsid protein of virus-infected isolates by probing nitrocellulose blots with mAb revealed diversity among immunoreactivity and in the size of the reactive capsid protein. Despite difficulties in visualizing virus within parasites by cross-section electron microscopy, gold-conjugated mAb readily labeled the cytoplasm of virus-positive trichomonads. Finally and importantly, isolates infecting patients attending an STD clinic, 75% of which were virus-positive isolates, had capsid protein of the same size detected by mAb present in all dsRNA viruses.

Adhesion in Candida spp

Microbial adherence is one of the most important determinants of pathogenesis, yet very few adhesins have been identified from fungal pathogens. Four structurally related adhesins, Hwp1, Ala1p/Als5p, Als1p, from Candida albicans and Epa1p from Candida glabrata, are members of a class of proteins termed glycosylphosphatidylinositol-dependent cell wall proteins (GPI-CWP). These proteins have N-terminal signal peptides and C-terminal features that mediate glycosylphosphatidylinositol (GPI) membrane anchor addition, as well as other determinants leading to attachment to cell wall glucan. While common signalP/GPI motifs facilitate cell surface expression, unique features mediate ligand binding specificities of adhesins. The first glimpse of structural features of putative adhesins has come from biophysical characterizations of the N-terminal domain of Als5p. One protein not in the GPI-CWP class that was initially described as an adhesin, Int1p, has recently been shown to be similar to Bud4p of Saccharomyces cerevisiae in primary amino acid sequence, in co-localizing with septins and in functioning in bud site selection. Progress in understanding the role of adhesins in oroesophageal candidiasis has been made for Hwp1 in a study using beige athymic and transgenic epsilon 26 mice that have combined defects in innate and acquired immune responses. Searches of the C. albicans genome for proteins in the GPI-CWP class has led to the identification of a subset of genes that will be the focus of future efforts to identify new Candida adhesins.