Molecular tools to regulate gene expression in Trypanosoma cruzi

Developing molecular strategies to manipulate gene expression in trypanosomatids is challenging, particularly with respect to the unique gene expression mechanisms adopted by these unicellular parasites, such as polycistronic mRNA transcription and multi-gene families. In the case of Trypanosoma cruzi (T. cruzi), the causative agent of Chagas Disease, the lack of RNA interference machinery further complicated functional genetic studies important for understanding parasitic biology and developing biomarkers and potential therapeutic targets. Therefore, alternative methods of performing knockout and/or endogenous labelling experiments were developed to identify and understand the function of proteins for survival and interaction with the host. In this review, we present the main tools for the genetic manipulation of T. cruzi, focusing on the Clustered Regularly Interspaced Short Palindromic Repeats Cas9-associated system technique widely used in this organism. Moreover, we highlight the importance of using these tools to elucidate the function of uncharacterized and glycosylated proteins. Further developments of these technologies will allow the identification of new biomarkers, therapeutic targets and potential vaccines against Chagas disease with greater efficiency and speed.

The protein map of the protozoan parasite Leishmania (Leishmania) amazonensis, Leishmania (Viannia) braziliensis and Leishmania (Leishmania) infantum during growth phase transition and temperature stress

Leishmania parasites cause a spectrum of diseases termed leishmaniasis, which manifests in two main clinical forms, cutaneous and visceral leishmaniasis. Leishmania promastigotes transit from proliferative exponential to quiescent stationary phases inside the insect vector, a relevant step that recapitulates early molecular events of metacyclogenesis. During the insect blood meal of the mammalian hosts, the released parasites interact initially with the skin, an event marked by temperature changes. Deep knowledge on the molecular events activated during Leishmania-host interactions in each step is crucial to develop better therapies and to understand the pathogenesis. In this study, the proteomes of Leishmania (Leishmania) amazonensis (La), Leishmania (Viannia) braziliensis (Lb), and Leishmania (Leishmania) infantum (syn L. L. chagasi) (Lc) were analyzed using quantitative proteomics to uncover the proteome modulation in three different conditions related to growth phases and temperature shifts: 1) exponential phase (Exp); 2) stationary phase (Sta25) and; 3) stationary phase subjected to heat stress (Sta34). Functional validations were performed using orthogonal techniques, focusing on α-tubulin, gp63 and heat shock proteins (HSPs). Species-specific and condition-specific modulation highlights the plasticity of the Leishmania proteome, showing that pathways related to metabolism and cytoskeleton are significantly modulated from exponential to stationary growth phases, while protein folding, unfolded protein binding, signaling and microtubule-based movement were differentially altered during temperature shifts. This study provides an in-depth proteome analysis of three Leishmania spp., and contributes compelling evidence of the molecular alterations of these parasites in conditions mimicking the interaction of the parasites with the insect vector and vertebrate hosts. SIGNIFICANCE: Leishmaniasis disease manifests in two main clinical forms according to the infecting Leishmania species and host immune responses, cutaneous and visceral leishmaniasis. In Brazil, cutaneous leishmaniasis (CL) is associated with L. braziliensis and L. amazonensis, while visceral leishmaniasis, also called kala-azar, is caused by L. infantum. Leishmania parasites remodel their proteomes during growth phase transition and changes in their mileu imposed by the host, including temperature. In this study, we performed a quantitative mass spectrometry-based proteomics to compare the proteome of three New world Leishmania species, L. amazonensis (La), L. braziliensis (Lb) and L. infantum (syn L. chagasi) (Lc) in three conditions: a) exponential phase at 25 °C (Exp); b) stationary phase at 25 °C (Sta25) and; c) stationary phase subjected to temperature stress at 34 °C (Sta34). This study provides an in-depth proteome analysis of three Leishmania spp. with varying pathophysiological outcomes, and contributes compelling evidence of the molecular alterations of these parasites in conditions mimicking the interaction of the parasites with the insect vector and vertebrate hosts.

A computational pipeline elucidating functions of conserved hypothetical Trypanosoma cruzi proteins based on public proteomic data

The proteome is complex, dynamic, and functionally diverse. Functional proteomics aims to characterize the functions of proteins in biological systems. However, there is a delay in annotating the function of proteins, even in model organisms. This gap is even greater in other organisms, including Trypanosoma cruzi, the causative agent of the parasitic, systemic, and sometimes fatal disease called Chagas disease. About 99.8% of Trypanosoma cruzi proteome is not manually annotated (unreviewed), among which>25% are conserved hypothetical proteins (CHPs), calling attention to the knowledge gap on the protein content of this organism. CHPs are conserved proteins among different species of various evolutionary lineages; however, they lack functional validation. This study describes a bioinformatics pipeline applied to public proteomic data to infer possible biological functions of conserved hypothetical Trypanosoma cruzi proteins. Here, the adopted strategy consisted of collecting differentially expressed proteins between the epimastigote and metacyclic trypomastigotes stages of Trypanosoma cruzi; followed by the functional characterization of these CHPs applying a manifold learning technique for dimension reduction and 3D structure homology analysis (Spalog). We found a panel of 25 and 26 upregulated proteins in the epimastigote and metacyclic trypomastigote stages, respectively; among these, 18 CHPs (8 in the epimastigote stage and 10 in the metacyclic stage) were characterized. The data generated corroborate the literature and complement the functional analyses of differentially regulated proteins at each stage, as they attribute potential functions to CHPs, which are frequently identified in Trypanosoma cruzi proteomics studies. However, it is important to point out that experimental validation is required to deepen our understanding of the CHPs.

Isolation of Extracellular Vesicles Using Titanium Dioxide Microspheres

Extracellular vesicles (EVs) are bilayer membrane particles released from several cell types to the extracellular environment. EVs have a crucial role in cell-cell communication, involving different biological processes in health and diseases. Due to the potential of biomarkers for several diseases as diagnostic and therapeutic tools, it is relevant to understand the biology of the EVs and their content. One of the current challenges involving EVs is regarding the purification method, which is a critical step for EV's functional and characterization studies. Ultracentrifugation is the most used method for EV isolation, where the nanoparticles are separated in sequential centrifugation to isolate the EVs based on their size. However, for viscous biofluids such as plasma, there is a co-isolation of the most abundant proteins, which can impair the EV's protein identification due to the low abundance of these proteins and signal suppression by the most abundant plasma proteins. Emerging techniques have gained attention in recent years. Titanium dioxide (TiO2) is one of the most promising techniques due to its property for selective isolation based on the interaction with phospholipids in the EV membrane. Using a small amount of TiO2 beads and a low volume of plasma, it is possible to isolate EVs with reduced plasma protein co-isolation. This study describes a comprehensive workflow for the isolation and characterization of plasma extracellular vesicles (EVs) using mass spectrometry-based proteomics techniques. The aim of this chapter is describe the EV isolation using TiO2 beads enrichment and high-throughput mass spectrometry techniques to efficiently identify the protein composition of EVs in a fast and straightforward manner.

Glycosort: A Computational Solution to Post-process Quantitative Large-Scale Intact Glycopeptide Analyses

Protein glycosylation is a post-translational modification involving the addition of carbohydrates to proteins and plays a crucial role in protein folding and various biological processes such as cell recognition, differentiation, and immune response. The vast array of natural sugars available allows the generation of plenty of unique glycan structures in proteins, adding complexity to the regulation and biological functions of glycans. The diversity is further increased by enzymatic site preferences and stereochemical conjugation, leading to an immense amount of different glycan structures. Understanding glycosylation heterogeneity is vital for unraveling the impact of glycans on different biological functions. Evaluating site occupancies and structural heterogeneity aids in comprehending glycan-related alterations in biological processes. Several software tools are available for large-scale glycoproteomics studies; however, integrating identification and quantitative data to assess heterogeneity complexity often requires extensive manual data processing. To address this challenge, we present a python script that automates the integration of Byonic and MaxQuant outputs for glycoproteomic data analysis. The script enables the calculation of site occupancy percentages by glycans and facilitates the comparison of glycan structures and site occupancies between two groups. This automated tool offers researchers a means to organize and interpret their high-throughput quantitative glycoproteomic data effectively.

Complement System Activation Is a Plasma Biomarker Signature during Malaria in Pregnancy

Malaria in pregnancy (MiP) is a public health problem in malaria-endemic areas, contributing to detrimental outcomes for both mother and fetus. Primigravida and second-time mothers are most affected by severe anemia complications and babies with low birth weight compared to multigravida women. Infected erythrocytes (IE) reach the placenta, activating the immune response by placental monocyte infiltration and inflammation. However, specific markers of MiP result in poor outcomes, such as low birth weight, and intrauterine growth restriction for babies and maternal anemia in women infected with Plasmodium falciparum are limited. In this study, we identified the plasma proteome signature of a mouse model infected with Plasmodium berghei ANKA and pregnant women infected with Plasmodium falciparum infection using quantitative mass spectrometry-based proteomics. A total of 279 and 249 proteins were quantified in murine and human plasma samples, of which 28% and 30% were regulated proteins, respectively. Most of the regulated proteins in both organisms are involved in complement system activation during malaria in pregnancy. CBA anaphylatoxin assay confirmed the complement system activation by the increase in C3a and C4a anaphylatoxins in the infected plasma compared to non-infected plasma. Moreover, correlation analysis showed the association between complement system activation and reduced head circumference in newborns from Pf-infected mothers. The data obtained in this study highlight the correlation between the complement system and immune and newborn outcomes resulting from malaria in pregnancy.

Glycoprotein molecular dynamics analysis: SARS-CoV-2 spike glycoprotein case study

Molecular Dynamics (MD) is a method used to calculate the movement of atoms and molecules broadly applied to several aspects of science. It involves computational simulation, which makes it, at first glance, not easily accessible. The rise of several automated tools to perform molecular simulations has allowed researchers to navigate through the various steps of MD. This enables to elucidate structural properties of proteins that could not be analyzed otherwise, such as the impact of glycosylation. Glycosylation dictates the physicochemical and biological properties of a protein modulating its solubility, stability, resistance to proteolysis, interaction partners, enzymatic activity, binding and recognition. Given the high conformational and compositional diversity of the glycan chains, assessing their influence on the protein structure is challenging using conventional analytical techniques. In this manuscript, we present a step-by-step workflow to build and perform MD analysis of glycoproteins focusing on the SPIKE glycoprotein of SARS-CoV-2 to appraise the impact of glycans in structure stabilization and antibody occlusion.

Systems-wide analysis of glycoprotein conformational changes by limited deglycosylation assay

A new method to probe the conformational changes of glycoproteins on a systems-wide scale, termed limited deglycosylation assay (LDA), is described. The method measures the differential rate of deglycosylation of N-glycans on natively folded proteins by the common peptide:N-glycosidase F (PNGase F) enzyme which in turn informs on their spatial presentation and solvent exposure on the protein surface hence ultimately the glycoprotein conformation. LDA involves 1) protein-level N-deglycosylation under native conditions, 2) trypsin digestion, 3) glycopeptide enrichment, 4) peptide-level N-deglycosylation and 5) quantitative MS-based analysis of formerly N-glycosylated peptides (FNGPs). LDA was initially developed and the experimental conditions optimized using bovine RNase B and fetuin. The method was then applied to glycoprotein extracts from LLC-MK2 epithelial cells upon treatment with dithiothreitol to induce endoplasmic reticulum stress and promote protein misfolding. Data from the LDA and 3D structure analysis showed that glycoproteins predominantly undergo structural changes in loops/turns upon ER stress as exemplified with detailed analysis of ephrin-A5, GALNT10, PVR and BCAM. These results show that LDA accurately reports on systems-wide conformational changes of glycoproteins induced under controlled treatment regimes. Thus, LDA opens avenues to study glycoprotein structural changes in a range of other physiological and pathophysiological conditions relevant to acute and chronic diseases. SIGNIFICANCE: We describe a novel method termed limited deglycosylation assay (LDA), to probe conformational changes of glycoproteins on a systems-wide scale. This method improves the current toolbox of structural proteomics by combining site and conformational-specific PNGase F enzymatic activity with large scale quantitative proteomics. X-ray crystallography, nuclear magnetic resonance spectroscopy and cryoEM techniques are the major techniques applied to elucidate macromolecule structures. However, the size and heterogeneity of the oligosaccharide chains poses several challenges to the applications of these techniques to glycoproteins. The LDA method presented here, can be applied to a range of pathophysiological conditions and expanded to investigate PTMs-mediated structural changes in complex proteomes.

The thermal proteome stability profile of Trypanosoma cruzi in epimastigote and trypomastigote life stages

Trypanosoma cruzi is a flagellate protozoa being the etiological agent of Chagas disease, a neglected tropical disease, which still poses a public health problem worldwide. The intricate molecular changes during T. cruzi-host interaction have been explored using different largescale omics techniques. However, protein stability is largely unknown. Thermal proteome profiling (TPP) methodology has the potential to characterize proteome-wide stability highlighting key proteins during T. cruzi infection and life stage transition from the invertebrate to the mammalian host. In the present work, T. cruzi epimastigotes and trypomastigotes cell lysates were subjected to TPP workflow and analyzed by quantitative large-scale mass spectrometry-based proteomics to fit a melting profile for each protein. A total of 2884 proteins were identified and associated to 1741 melting curves being 1370 in trypomastigotes (Tm_AVG 53.53 °C) and 1279 in epimastigotes (Tm_AVG 50.89 °C). A total of 453 proteins were identified with statistically different melting profiles between the two life stages. Proteins associated to pathogenesis and intracellular transport had regulated melting temperatures. Membrane and glycosylated proteins had a higher average Tm in trypomastigotes compared to epimastigotes. This study represents the first large-scale comparison of parasite protein stability between life stages. SIGNIFICANCE: Trypanosoma cruzi, a unicellular flagellate parasite, is the etiological agent of Chagas disease, endemic in South America and affecting more that 7 million people worldwide. There is an intense research to identify novel chemotherapeutic and diagnostic targets of Chagas disease. Proteomic approaches have helped in elucidating the quantitative proteome and PTMs changes of T. cruzi during life cycle transition and upon different biotic and abiotic stimuli. However, a comprehensive knowledge of the protein-protein interaction and protein conformation is still missing. In order to fill this gap, this manuscript elucidates the T. cruzi Y strain proteome-wide thermal stability map in the epimastigote and trypomastigote life stages. Comparison between life stages showed a higher average melting temperature stability for trypomastigotes than epimastigotes indicating a host temperature adaptation. Both presented a selective thermal stability shift for cellular compartments, molecular functions and biological processes based on the T. cruzi life stage. Membrane and glycosylated proteins presented a higher thermal stability in trypomastigotes when compared to the epimastigotes.

HSPB1 influences mitochondrial respiration in ER-stressed beta cells

Beta-cell death and dysfunction are involved in the development of type 1 and 2 diabetes. ER-stress impairs beta-cells function resulting in pro-apoptotic stimuli that promote cell death. Hence, the identification of protective mechanisms in response to ER-stress could lead to novel therapeutic targets and insight in the pathology of these diseases. Here, we report the identification of proteins involved in dysregulated pathways upon thapsigargin treatment of MIN6 cells. Utilizing quantitative proteomics we identified upregulation of proteins involved in protein folding, unfolded protein response, redox homeostasis, proteasome processes associated with endoplasmic reticulum and downregulation of TCA cycle, cellular respiration, lipid metabolism and ribosome assembly processes associated to mitochondria and eukaryotic initiation translation factor components. Subsequently, pro-inflammatory cytokine treatment was performed to mimic pathological changes observed in beta-cells during diabetes. Cytokines induced ER stress and impaired mitochondrial function in beta-cells corroborating the results obtained with the proteomic approach. HSPB1 levels are increased by prolactin on pancreatic beta-cells and this protein is a key factor for cytoprotection although its role has not been fully elucidated. Here we show that while up-regulation of HSPB1 was able to restore the mitochondrial dysfunction induced by beta-cells' exposure to inflammatory cytokines, silencing of this chaperone abrogated the beneficial effects promoted by PRL. Taken together, our results outline the importance of HSPB1 to mitigate beta-cell dysfunction. Further studies are needed to elucidate its role in diabetes.

The Role of Sialic Acids in the Establishment of Infections by Pathogens, With Special Focus on Leishmania

Carbohydrates or glycans are ubiquitous components of the cell surface which play crucial biological and structural roles. Sialic acids (Sias) are nine-carbon atoms sugars usually present as terminal residues of glycoproteins and glycolipids on the cell surface or secreted. They have important roles in cellular communication and also in infection and survival of pathogens. More than 20 pathogens can synthesize or capture Sias from their hosts and incorporate them into their own glycoconjugates and derivatives. Sialylation of pathogens’ glycoconjugates may be crucial for survival inside the host for numerous reasons. The role of Sias in protozoa such as Trypanosoma and Leishmania was demonstrated in previous studies. This review highlights the importance of Sias in several pathogenic infections, focusing on Leishmania. We describe in detail the contributions of Sias, Siglecs (sialic acid binding Ig-like lectins) and Neuraminidase 1 (NEU 1) in the course of Leishmania infection. A detailed view on the structural and functional diversity of Leishmania-related Sias and host-cell receptors will be provided, as well as the results of functional studies performed with different Leishmania species.

PhyloQuant approach provides insights into Trypanosoma cruzi evolution using a systems-wide mass spectrometry-based quantitative protein profile

The etiological agent of Chagas disease, Trypanosoma cruzi, is a complex of seven genetic subdivisions termed discrete typing units (DTUs), TcI-TcVI and Tcbat. The relevance of T. cruzi genetic diversity to the variable clinical course of the disease, virulence, pathogenicity, drug resistance, transmission cycles and ecological distribution requires understanding the parasite origin and population structure. In this study, we introduce the PhyloQuant approach to infer the evolutionary relationships between organisms based on differential mass spectrometry-based quantitative features. In particular, large scale quantitative bottom-up proteomics features (MS1, iBAQ and LFQ) were analyzed using maximum parsimony, showing a correlation between T. cruzi DTUs and closely related trypanosomes' protein expression and sequence-based clustering. Character mapping enabled the identification of synapomorphies, herein the proteins and their respective expression profiles that differentiate T. cruzi DTUs and trypanosome species. The distance matrices based on phylogenetics and PhyloQuant clustering showed statistically significant correlation highlighting the complementarity between the two strategies. Moreover, PhyloQuant allows the identification of differentially regulated and strain/DTU/species-specific proteins, and has potential application in the identification of specific biomarkers and candidate therapeutic targets.

Protein glycosylation inLeishmaniaspp

Protein glycosylation is a co- and post-translational modification that, inLeishmaniaparasites, plays key roles in vector–parasite–vertebrate host interaction.

Proteomics and Leishmaniasis: Potential Clinical Applications

Leishmaniases are diseases caused by protozoan parasites of the genus Leishmania. They are endemic in 98 countries, affect around 12 million people worldwide and may present several distinct clinical forms. Unfortunately, there are only a few drugs available for treatment of leishmaniasis, which are toxic and not always effective. Different parasite species and different clinical forms require optimization of the treatment or more specific therapies, which are not available. The emergence of resistance is also a matter of concern. Besides, diagnosis can sometimes be complicated due to atypical manifestations and associations with other pathologies. In this review, proteomic data are presented and discussed in terms of their application in important issues in leishmaniasis such as parasite resistance to chemotherapy, diagnosis of active disease in patients and dogs, markers for different clinical forms, identification of virulence factors, and their potential use in vaccination. It is shown that proteomics has contributed to the discovery of potential biomarkers for prognosis, diagnosis, therapeutics, monitoring of disease progression, treatment follow-up and identification of vaccine candidates for specific diseases. However, the authors believe its capabilities have not yet been fully explored for routine clinical analysis for several reasons, which will be presented in this review.