RESUMEN
Free-living amoeba (FLA) group includes the potentially pathogenic genera Acanthamoeba, Naegleria, Balamuthia, Sappinia, and Vermamoeba, causative agents of human infections (encephalitis, keratitis, and disseminated diseases). In Brazil, the first report on pathogenic FLA was published in the 70s and showed meningoencephalitis caused by Naegleria spp. FLA studies are emerging, but no literature review is available to investigate this trend in Brazil critically. Thus, the present work aims to integrate and discuss these data. Scopus, PubMed, and Web of Science were searched, retrieving studies from 1974 to 2020. The screening process resulted in 178 papers, which were clustered into core and auxiliary classes and sorted into five categories: wet-bench studies, dry-bench studies, clinical reports, environmental identifications, and literature reviews. The papers dating from the last ten years account for 75% (134/178) of the total publications, indicating the FLA topic has gained Brazilian interest. Moreover, 81% (144/178) address Acanthamoeba-related matter, revealing this genus as the most prevalent in all categories. Brazil's Southeast, South, and Midwest geographic regions accounted for 96% (171/178) of the publications studied in the present work. To the best of our knowledge, this review is the pioneer in summarising the FLA research history in Brazil.
Asunto(s)
Acanthamoeba , Amoeba , Encefalitis , Brasil , Movimiento Celular , HumanosRESUMEN
Chromatin associated proteins are key regulators of many important processes in the cell. Trypanosoma cruzi, a protozoa flagellate that causes Chagas disease, alternates between replicative and nonreplicative forms accompanied by a shift on global transcription levels and by changes in its chromatin architecture. Here, we investigated the T. cruzi chromatin proteome using three different protocols and compared it between replicative (epimastigote) and nonreplicative (trypomastigote) forms by high-resolution mass spectrometry. More than 2000 proteins were identified and quantified both in chromatin and nonchromatin extracts. Besides histones and other known nuclear proteins, trypanosomes chromatin also contains metabolic (mainly from carbohydrate pathway), cytoskeleton and many other proteins with unknown functions. Strikingly, the two parasite forms differ greatly regarding their chromatin-associated factors composition and amount. Although the nucleosome content is the same for both life forms (as seen by MNase digestion), the remaining proteins were much less detected in nonreplicative forms, suggesting that they have a naked chromatin. Proteins associated to DNA proliferation, such as PCNA, RPA, and DNA topoisomerases were exclusively found in the chromatin of replicative stages. On the other hand, the nonreplicative stages have an enrichment of a histone H2B variant. Furthermore, almost 20% of replicative stages chromatin-associated proteins are expressed in nonreplicative forms, but located at nonchromatin space. We identified different classes of proteins including phosphatases and a Ran-binding protein, that may shuttle between chromatin and nonchromatin space during differentiation. Seven proteins, including those with unknown functions, were selected for further validation. We confirmed their location in chromatin and their differential expression, using Western blotting assays and chromatin immunoprecipitation (ChIP). Our results indicate that the replicative state in trypanosomes involves an increase of chromatin associated proteins content. We discuss in details, the qualitative and quantitative implication of this chromatin set in trypanosome chromatin biology. Because trypanosomes are early-branching organisms, this data can boost our understanding of chromatin-associated processes in other cell types.
Asunto(s)
Cromatina/metabolismo , Proteómica/métodos , Proteínas Protozoarias/metabolismo , Trypanosoma cruzi/fisiología , Línea Celular , Cromatografía Liquida , Humanos , Estadios del Ciclo de Vida , Espectrometría de Masas en Tándem , Trypanosoma cruzi/metabolismoRESUMEN
Selenium (Se) is an essential trace element for several organisms and is mostly present in proteins as L-selenocysteine (Sec or U). Sec is synthesized on its L-seryl-tRNASec to produce Sec-tRNASec molecules by a dedicated selenocysteine synthesis machinery and incorporated into selenoproteins at specified in-frame UGA codons. UGA-Sec insertion is signaled by an mRNA stem-loop structure called the SElenoCysteine Insertion Sequence (SECIS). tRNASec transcription regulation and folding have been described showing its importance to Sec biosynthesis. Here, we discuss structural aspects of Sec-tRNASec and its role in Sec biosynthesis as well as Sec incorporation into selenoproteins. Defects in the Sec biosynthesis or incorporation pathway have been correlated with pathological conditions.
Asunto(s)
ARN de Transferencia de Cisteína/genética , Selenocisteína/biosíntesis , Animales , Codón de Terminación/química , Codón de Terminación/genética , Codón de Terminación/metabolismo , Humanos , Biosíntesis de Proteínas , ARN Mensajero/química , ARN Mensajero/genética , ARN Mensajero/metabolismo , ARN de Transferencia de Cisteína/química , ARN de Transferencia de Cisteína/metabolismo , Selenocisteína/genéticaRESUMEN
Naegleria fowleri is a pathogenic amoeboflagellate most prominently known for its role as the etiological agent of the Primary Amoebic Meningoencephalitis (PAM), a disease that afflicts the central nervous system and is fatal in more than 95% of the reported cases. Although being fatal and with potential risks for an increase in the occurrence of the pathogen in populated areas, the organism receives little public health attention. A great underestimation in the number of PAM cases reported is assumed, taking into account the difficulty in obtaining an accurate diagnosis. In this review, we summarize different techniques and methods used in the identification of the protozoan in clinical and environmental samples. Since it remains unclear whether the protozoan infection can be successfully treated with the currently available drugs, we proceed to discuss the current PAM therapeutic strategies and its effectiveness. Finally, novel compounds for potential treatments are discussed as well as research on vaccine development against PAM.
Asunto(s)
Infecciones Protozoarias del Sistema Nervioso Central/terapia , Naegleria fowleri/fisiología , Antiprotozoarios/uso terapéutico , Infecciones Protozoarias del Sistema Nervioso Central/diagnóstico , Infecciones Protozoarias del Sistema Nervioso Central/prevención & control , Agua Potable/parasitología , Agua Potable/normas , Humanos , Naegleria fowleri/genética , Factores de Riesgo , VacunaciónRESUMEN
Histones are well-conserved proteins that form the basic structure of chromatin in eukaryotes and undergo several post-translational modifications, which are important for the control of transcription, replication, DNA damage repair, and chromosome condensation. In early branched organisms, histones are less conserved and appear to contain alternative sites for modifications, which could reveal evolutionary unique functions of histone modifications in gene expression and other chromatin-based processes. Here, by using high-resolution mass spectrometry, we identified and quantified histone post-translational modifications in two life cycle stages of Trypanosoma cruzi, the protozoan parasite that causes Chagas disease. We detected 44 new modifications, namely: 18 acetylations, seven monomethylations, seven dimethylations, seven trimethylations, and four phosphorylations. We found that replicative (epimastigote stage) contains more histone modifications than nonreplicative and infective parasites (trypomastigote stage). Acetylations of lysines at the C-terminus of histone H2A and methylations of lysine 23 of histone H3 were found to be enriched in trypomastigotes. In contrast, phosphorylation in serine 23 of H2B and methylations of lysine 76 of histone H3 predominates in proliferative states. The presence of one or two methylations in the lysine 76 was found in cells undergoing mitosis and cytokinesis, typical of proliferating parasites. Our findings provide new insights into the role of histone modifications related to the control of gene expression and cell-cycle regulation in an early divergent organism.
Asunto(s)
Cromatina/química , Código de Histonas , Estadios del Ciclo de Vida , Proteómica/métodos , Acetilación , Ciclo Celular , Regulación de la Expresión Génica , Metilación , Fosforilación , Procesamiento Proteico-Postraduccional/fisiología , Trypanosoma cruziRESUMEN
Chagas disease, Sleeping Sickness, Nagana and Leishmaniasis are serious infections caused by protozoa of the order Kinetoplastidae. They were described over a century ago by seminal work of different physician-researchers and, despite the initial discoveries, few drugs have been made available for the treatment of these infections. The drugs available present serious efficacy and toxicity problems. Moreover, the emergence of resistant strains has rendered the development of novel chemotherapeutic strategies a priority. Auranofin is currently in use to treat rheumatoid arthritis in humans. Previous reports showed that this compound presents activity against Trypanosoma brucei and Leishmania cells. In Trypanosoma cruzi cells, auranofin resulted in a more potent compound than benznidazole in vitro when tested in different DTUs. In vivo experiments, although not decreasing T. cruzi parasitemia, decreases host mortality. Therefore, we propose auranofin as a potential alternative for a new chemotherapy in Chagas disease with the added advantage of already being approved for use in humans.
Asunto(s)
Auranofina/farmacología , Enfermedad de Chagas/tratamiento farmacológico , Tripanocidas/farmacología , Trypanosoma cruzi/efectos de los fármacos , Animales , Antirreumáticos/farmacología , Antirreumáticos/uso terapéutico , Auranofina/uso terapéutico , Línea Celular , Enfermedad de Chagas/parasitología , Femenino , Fibroblastos/parasitología , Humanos , Concentración 50 Inhibidora , Dosificación Letal Mediana , Ratones , Ratones Endogámicos BALB C , Nitroimidazoles/farmacología , Parasitemia/tratamiento farmacológico , Parasitemia/parasitología , Distribución Aleatoria , Organismos Libres de Patógenos Específicos , Tripanocidas/uso terapéuticoRESUMEN
The 21st amino acid, selenocysteine (Sec), is synthesized on its dedicated transfer RNA (tRNASec). In bacteria, Sec is synthesized from Ser-tRNA[Ser]Sec by Selenocysteine Synthase (SelA), which is a pivotal enzyme in the biosynthesis of Sec. The structural characterization of bacterial SelA is of paramount importance to decipher its catalytic mechanism and its role in the regulation of the Sec-synthesis pathway. Here, we present a comprehensive single-particle cryo-electron microscopy (SPA cryoEM) structure of the bacterial SelA with an overall resolution of 2.69 Å. Using recombinant Escherichia coli SelA, we purified and prepared samples for single-particle cryoEM. The structural insights from SelA, combined with previous in vivo and in vitro knowledge, underscore the indispensable role of decamerization in SelA's function. Moreover, our structural analysis corroborates previous results that show that SelA adopts a pentamer of dimers configuration, and the active site architecture, substrate binding pocket, and key K295 catalytic residue are identified and described in detail. The differences in protein architecture and substrate coordination between the bacterial enzyme and its counterparts offer compelling structural evidence supporting the independent molecular evolution of the bacterial and archaea/eukarya Ser-Sec biosynthesis present in the natural world.
RESUMEN
Selenocysteine Synthase (SELA, E.C. 2.9.1.1) from Escherichia coli is a homodecamer pyridoxal-5'-phosphate containing enzyme responsible for the conversion of seryl-tRNA(sec) into selenocysteyl-tRNA(sec) in the biosynthesis of the 21th amino acid, selenocysteine (Sec or U). This paper describes the cloning of the E. coli selA gene into a modified pET29a(+) vector and its expression in E. coli strain WL81460, a crucial modification allowing SELA expression without bound endogenous tRNA(sec). This expression strategy enabled the purification and additional biochemical and biophysical characterization of the SELA decamer. The homogeneous SELA protein was obtained using three chromatographic steps. Size Exclusion Chromatography and Native Gel Electrophoresis showed that SELA maintains a decameric state with molecular mass of approximately 500 kDa with an isoelectric point of 6,03. A predominance of α-helix structures was detected by circular dichroism with thermal stability up to 45 °C. The oligomeric assemblage of SELA was investigated by glutaraldehyde crosslinking experiments indicate that SELA homodecameric structure is the result of a stepwise addition of intermediate oligomeric states and not a direct monomer to homodecamer transition. Our results have contributed to the establishment of a robust expression model for the enzyme free of bound RNA and are of general interest to be taken into consideration in all cases of heterologous/homologous expressions of RNA-binding proteins avoiding the carryover of endogenous RNAs, which may interfere with further biochemical characterizations.
Asunto(s)
Escherichia coli/enzimología , Proteínas Recombinantes/aislamiento & purificación , Transferasas/química , Transferasas/aislamiento & purificación , Biofisica , Peso Molecular , Estructura Secundaria de Proteína , Fosfato de Piridoxal/química , ARN de Transferencia Aminoácido-Específico/química , Proteínas Recombinantes/biosíntesis , Proteínas Recombinantes/química , Selenocisteína/biosíntesis , Selenocisteína/químicaRESUMEN
Selenophosphate synthetase (SPS) plays an indispensable role in selenium metabolism, being responsible for catalyzing the activation of selenide with adenosine 5'-triphosphate (ATP) to generate selenophosphate, the essential selenium donor for selenocysteine synthesis. Recombinant full-length Leishmania major SPS (LmSPS2) was recalcitrant to crystallization. Therefore, a limited proteolysis technique was used and a stable N-terminal truncated construct (ΔN-LmSPS2) yielded suitable crystals. The Trypanosoma brucei SPS orthologue (TbSPS2) was crystallized by the microbatch method using paraffin oil. X-ray diffraction data were collected to resolutions of 1.9 Å for ΔN-LmSPS2 and 3.4 Å for TbSPS2.
Asunto(s)
Leishmania major , Fosfotransferasas/química , Proteínas Protozoarias/química , Trypanosoma brucei brucei , Cristalización , Difracción de Rayos XRESUMEN
Epigenetic marks enable cells to acquire new biological features that favor their adaptation to environmental changes. These marks are chemical modifications on chromatin-associated proteins and nucleic acids that lead to changes in the chromatin landscape and may eventually affect gene expression. The chemical tags of these epigenetic marks are comprised of intermediate cellular metabolites. The number of discovered associations between metabolism and epigenetics has increased, revealing how environment influences gene regulation and phenotype diversity. This connection is relevant to all organisms but underappreciated in digenetic parasites, which must adapt to different environments as they progress through their life cycles. This review speculates and proposes associations between epigenetics and metabolism in trypanosomes, which are protozoan parasites that cause human and livestock diseases.
Asunto(s)
Epigénesis Genética , Trypanosoma , Humanos , Cromatina , Trypanosoma/genéticaRESUMEN
Protein tyrosine phosphatases (PTPs) are key virulence factors in pathogenic bacteria, consequently, they have become important targets for new approaches against these pathogens, especially in the fight against antibiotic resistance. Among these targets of interest YopH (Yersinia outer protein H) from virulent species of Yersinia is an example. PTPs can be reversibly inhibited by nitric oxide (NO) since the oxidative modification of cysteine residues may influence the protein structure and catalytic activity. We therefore investigated the effects of NO on the structure and enzymatic activity of Yersinia enterocolitica YopH in vitro. Through phosphatase activity assays, we observe that in the presence of NO YopH activity was inhibited by 50%, and that this oxidative modification is partially reversible in the presence of DTT. Furthermore, YopH S-nitrosylation was clearly confirmed by a biotin switch assay, high resolution mass spectrometry (MS) and X-ray crystallography approaches. The crystal structure confirmed the S-nitrosylation of the catalytic cysteine residue, Cys403, while the MS data provide evidence that Cys221 and Cys234 might also be modified by NO. Interestingly, circular dichroism spectroscopy shows that the S-nitrosylation affects secondary structure of wild type YopH, though to a lesser extent on the catalytic cysteine to serine YopH mutant. The data obtained demonstrate that S-nitrosylation inhibits the catalytic activity of YopH, with effects beyond the catalytic cysteine. These findings are helpful for designing effective YopH inhibitors and potential therapeutic strategies to fight this pathogen or others that use similar mechanisms to interfere in the signal transduction pathways of their hosts.
Asunto(s)
Proteínas de la Membrana Bacteriana Externa/química , Cisteína/química , Óxido Nítrico/química , Proteínas Tirosina Fosfatasas/química , Proteínas de la Membrana Bacteriana Externa/metabolismo , Biotina/metabolismo , Catálisis , Cristalografía por Rayos X/métodos , Cisteína/metabolismo , Humanos , Espectrometría de Masas/métodos , Estructura Molecular , Óxido Nítrico/metabolismo , Oxidación-Reducción , Proteínas Tirosina Fosfatasas/metabolismo , Transducción de Señal , Yersinia enterocolitica/metabolismoRESUMEN
Several molecular mechanisms are involved in the genetic code interpretation during translation, as codon degeneration for the incorporation of rare amino acids. One mechanism that stands out is selenocysteine (Sec), which requires a specific biosynthesis and incorporation pathway. In Bacteria, the Sec biosynthesis pathway has unique features compared with the eukaryote pathway as Ser to Sec conversion mechanism is accomplished by a homodecameric enzyme (selenocysteine synthase, SelA) followed by the action of an elongation factor (SelB) responsible for delivering the mature Sec-tRNASec into the ribosome by the interaction with the Selenocysteine Insertion Sequence (SECIS). Besides this mechanism being already described, the sequential events for Sec-tRNASec and SECIS specific recognition remain unclear. In this study, we determined the order of events of the interactions between the proteins and RNAs involved in Sec incorporation. Dissociation constants between SelB and the native as well as unacylated-tRNASec variants demonstrated that the acceptor stem and variable arm are essential for SelB recognition. Moreover, our data support the sequence of molecular events where GTP-activated SelB strongly interacts with SelA.tRNASec. Subsequently, SelB.GTP.tRNASec recognizes the mRNA SECIS to deliver the tRNASec to the ribosome. SelB in complex with its specific RNAs were examined using Hydrogen/Deuterium exchange mapping that allowed the determination of the molecular envelopes and its secondary structural variations during the complex assembly. Our results demonstrate the ordering of events in Sec incorporation and contribute to the full comprehension of the tRNASec role in the Sec amino acid biosynthesis, as well as extending the knowledge of synthetic biology and the expansion of the genetic code.
Asunto(s)
Escherichia coli/genética , Escherichia coli/metabolismo , Regulación Bacteriana de la Expresión Génica , Factores de Elongación de Péptidos/metabolismo , ARN de Transferencia Aminoácido-Específico/metabolismo , Selenocisteína/metabolismo , Unión Proteica , ARN Mensajero/genéticaRESUMEN
tRNA synthetases are responsible for decoding the molecular information, from codons to amino acids. Seryl-tRNA synthetase (SerRS), besides the five isoacceptors of tRNASer, recognizes tRNA[Ser]Sec for the incorporation of selenocysteine (Sec, U) into selenoproteins. The selenocysteine synthesis pathway is known and is dependent on several protein-protein and protein-RNA interactions. Those interactions are not fully described, in particular, involving tRNA[Ser]Sec and SerRS. Here we describe the molecular interactions between the Escherichia coli Seryl-tRNA synthetase (EcSerRS) and tRNA[Ser]Sec in order to determine their specificity, selectivity and binding order, leading to tRNA aminoacylation. The dissociation constant of EcSerRS and tRNA[Ser]Sec was determined as (126 ± 20) nM. We also demonstrate that EcSerRS binds initially to tRNA[Ser]Sec in the presence of ATP for further recognition by E. coli selenocysteine synthetase (EcSelA) for Ser to Sec conversion. The proposed studies clarify the mechanism of tRNA[Ser]Sec incorporation in Bacteria as well as of other domains of life.
Asunto(s)
Escherichia coli/metabolismo , Regulación Bacteriana de la Expresión Génica , ARN de Transferencia Aminoácido-Específico/metabolismo , ARN de Transferencia de Cisteína/metabolismo , Serina-ARNt Ligasa/metabolismo , Transferasas/metabolismo , Adenosina Trifosfato/metabolismo , Sitios de Unión , Escherichia coli/genética , Cinética , Modelos Moleculares , Unión Proteica , Conformación Proteica en Hélice alfa , Conformación Proteica en Lámina beta , Dominios y Motivos de Interacción de Proteínas , ARN de Transferencia Aminoácido-Específico/genética , ARN de Transferencia de Cisteína/genética , Serina-ARNt Ligasa/genética , Termodinámica , Aminoacilación de ARN de Transferencia/genética , Transferasas/genéticaRESUMEN
The genus Naegleria, of the free-living amoeba (FLA) group, has been investigated mainly due to its human health impact, resulting in deadly infections and their worldwide distribution on freshwater systems. Naegleria fowleri, colloquially known as the "brain-eating amoeba," is the most studied Naegleria species because it causes primary amoebic meningoencephalitis (PAM) of high lethality. The assessment of FLA biodiversity is fundamental to evaluate the presence of pathogenic species and the possibility of human contamination. However, the knowledge of FLA distribution in Brazil is unknown, and to rectify this situation, we present research on identifying Naegleria spp. in the Monjolinho River as a model study. The river is a public Brazilian freshwater source that crosses the city of São Carlos, in São Paulo state, Brazil. Five distinct sampling sites were examined through limnological features, trophozoites culturing, and PCR against internal transcribed spacer (ITS) regions and 5.8S rRNA sequences. The results identified N. philippinensis, N. canariensisi, N. australiensis, N. gruberi, N. dobsoni sequences, as well as a Hartmannella sequence. The methodology delineated here represents the first Brazilian Naegleria spp. study on a freshwater system. Our results stress the urgency of a large scale evaluation of the presence of free-living amoebas in Brazil.
RESUMEN
Eukaryotes from the Excavata superphylum have been used as models to study the evolution of cellular molecular processes. Strikingly, human parasites of the Trypanosomatidae family (T. brucei, T. cruzi and L. major) conserve the complex machinery responsible for selenocysteine biosynthesis and incorporation in selenoproteins (SELENOK/SelK, SELENOT/SelT and SELENOTryp/SelTryp), although these proteins do not seem to be essential for parasite viability under laboratory controlled conditions. Selenophosphate synthetase (SEPHS/SPS) plays an indispensable role in selenium metabolism, being responsible for catalyzing the formation of selenophosphate, the biological selenium donor for selenocysteine synthesis. We solved the crystal structure of the L. major selenophosphate synthetase and confirmed that its dimeric organization is functionally important throughout the domains of life. We also demonstrated its interaction with selenocysteine lyase (SCLY) and showed that it is not present in other stable assemblies involved in the selenocysteine pathway, namely the phosphoseryl-tRNASec kinase (PSTK)-Sec-tRNASec synthase (SEPSECS) complex and the tRNASec-specific elongation factor (eEFSec) complex. Endoplasmic reticulum stress with dithiothreitol (DTT) or tunicamycin upon selenophosphate synthetase ablation in procyclic T. brucei cells led to a growth defect. On the other hand, only DTT presented a negative effect in bloodstream T. brucei expressing selenophosphate synthetase-RNAi. Furthermore, selenoprotein T (SELENOT) was dispensable for both forms of the parasite. Together, our data suggest a role for the T. brucei selenophosphate synthetase in the regulation of the parasite's ER stress response.
Asunto(s)
Liasas/metabolismo , Fosfotransferasas/metabolismo , Selenocisteína/biosíntesis , Selenoproteínas/metabolismo , Trypanosoma brucei brucei/enzimología , Conformación Proteica , Proteínas Protozoarias/metabolismo , Selenio/metabolismoRESUMEN
The dichloromethane extract of Calea uniflora afforded a mixture of two novel chromanones, uniflorol-A (1) and uniflorol-B (2), and one known chromanone, 2,2-dimethyl-6-(1-hydroxyethyl)-chroman-4-one (3). The structures of these compounds were determined by spectroscopic methods. Biological activity of the compounds against Leishmania major promastigotes was evaluated. Mixture of the novel chromanones 1 and 2 showed significant growth inhibition of the parasite in the micrograms per milliliter range.
Asunto(s)
Antraquinonas/aislamiento & purificación , Antiprotozoarios/aislamiento & purificación , Asteraceae/química , Leishmania major/efectos de los fármacos , Raíces de Plantas/química , Animales , Antraquinonas/química , Antraquinonas/farmacología , Antiprotozoarios/química , Antiprotozoarios/farmacología , Cromonas , Extractos Vegetales/química , Extractos Vegetales/aislamiento & purificación , Extractos Vegetales/farmacologíaRESUMEN
Free-living amoeba (FLA) group includes the potentially pathogenic genera Acanthamoeba, Naegleria, Balamuthia, Sappinia, and Vermamoeba, causative agents of human infections (encephalitis, keratitis, and disseminated diseases). In Brazil, the first report on pathogenic FLA was published in the 70s and showed meningoencephalitis caused by Naegleria spp. FLA studies are emerging, but no literature review is available to investigate this trend in Brazil critically. Thus, the present work aims to integrate and discuss these data. Scopus, PubMed, and Web of Science were searched, retrieving studies from 1974 to 2020. The screening process resulted in 178 papers, which were clustered into core and auxiliary classes and sorted into five categories: wet-bench studies, dry-bench studies, clinical reports, environmental identifications, and literature reviews. The papers dating from the last ten years account for 75% (134/178) of the total publications, indicating the FLA topic has gained Brazilian interest. Moreover, 81% (144/178) address Acanthamoeba-related matter, revealing this genus as the most prevalent in all categories. Brazil's Southeast, South, and Midwest geographic regions accounted for 96% (171/178) of the publications studied in the present work. To the best of our knowledge, this review is the pioneer in summarising the FLA research history in Brazil.
RESUMEN
Selenium is an essential trace element which, at adequate levels, presents different beneficial biological effects, such as cancer regression, tissue development and protection against oxidative damage. The positive effects of this element are related to the expression of selenoproteins and their ability to modulate the immune system and the oxidative stress response. In Chagas disease and sleeping sickness, selenium supplementation has shown blood parasitism reduction and the alleviation of specific aspects of the diseases, such as diminishing anemia in sleeping sickness or minimization of myocardial and right ventricular chamber damage in Chagas disease. Although the influence of selenium in trypanosomiasis has been investigated, the direct effects of sodium selenite supplementation on trypanosome cells are poorly understood. Treatment of Trypanosoma cruzi cultures with low selenium doses demonstrated different results, according to the parasite evolutive form analyzed. Epimastigote cultures supplemented with 100 nM of sodium selenite presented cell growth increment, which varies from 10 to 40% according to the parasite strain assayed. Selenium concentration around 600nM leads to a 30% increase in the amastigote form number, whereas, at the same dose, the mammal host cell presented no cellular growth alteration. For the bloodstream form, the results agree with the literature, and all sodium selenite concentrations tested, demonstrated a reduction in parasite viability. The data suggest that selenium supplementation, under specific conditions, could increase T. cruzi viability, demonstrating that a strategy for using selenium as an adjuvant in Chagas disease treatment requires additional experimentation.
Asunto(s)
Selenio , Trypanosoma cruzi , Enfermedad de Chagas , Selenito de SodioRESUMEN
Leishmania RNA Virus (LRV, Totiviridae) infect Leishmania cells and subvert mice immune response, probably promoting parasite persistence, suggesting significant roles for LRV in host-parasite interaction. Here we describe a new LRV1-4 purification protocol, enabling capsid visualization by negatively stained electron microscopy representing a significant contribution to future LRV investigations.
Asunto(s)
Leishmaniavirus/aislamiento & purificación , Virión/aislamiento & purificación , Virología/métodos , Leishmaniavirus/ultraestructura , Microscopía Electrónica de Transmisión , Coloración y Etiquetado/métodos , Virión/ultraestructuraRESUMEN
Xylella fastidiosa is responsible for a wide range of economically important plant diseases. We report here the crystal structure and kinetic data of Xylellain, the first cysteine protease characterized from the genome of the pathogenic X. fastidiosa strain 9a5c. Xylellain has a papain-family fold, and part of the N-terminal sequence blocks the enzyme active site, thereby mediating protein activity. One novel feature identified in the structure is the presence of a ribonucleotide bound outside the active site. We show that this ribonucleotide plays an important regulatory role in Xylellain enzyme kinetics, possibly functioning as a physiological mediator.