APEX2-based proximity proteomic analysis identifies candidate interactors for Plasmodium falciparum knob-associated histidine-rich protein in infected erythrocytes.

The interaction of Plasmodium falciparum-infected red blood cells (iRBCs) with the vascular endothelium plays a crucial role in malaria pathology and disease. KAHRP is an exported P. falciparum protein involved in iRBC remodelling, which is essential for the formation of protrusions or "knobs" on the iRBC surface. These knobs and the proteins that are concentrated within them allow the parasites to escape the immune response and host spleen clearance by mediating cytoadherence of the iRBC to the endothelial wall, but this also slows down blood circulation, leading in some cases to severe cerebral and placental complications. In this work, we have applied genetic and biochemical tools to identify proteins that interact with P. falciparum KAHRP using enhanced ascorbate peroxidase 2 (APEX2) proximity-dependent biotinylation and label-free shotgun proteomics. A total of 30 potential KAHRP-interacting candidates were identified, based on the assigned fragmented biotinylated ions. Several identified proteins have been previously reported to be part of the Maurer's clefts and knobs, where KAHRP resides. This study may contribute to a broader understanding of P. falciparum protein trafficking and knob architecture and shows for the first time the feasibility of using APEX2-proximity labelling in iRBCs.

Anti-Protozoan Activities of Polar Fish-Derived Polyalanine Synthetic Peptides.

Chagas disease, sleeping sickness and malaria are infectious diseases caused by protozoan parasites that kill millions of people worldwide. Here, we performed in vitro assays of Pa-MAP, Pa-MAP1.9, and Pa-MAP2 synthetic polyalanine peptides derived from the polar fish Pleuronectes americanus toward Trypanosoma cruzi, T. brucei gambiense and Plasmodium falciparum activities. We demonstrated that the peptides Pa-MAP1.9 and Pa-MAP2 were effective to inhibit T. brucei growth. In addition, structural analyses using molecular dynamics (MD) studies showed that Pa-MAP2 penetrates deeper into the membrane and interacts more with phospholipids than Pa-MAP1.9, corroborating the previous in vitro results showing that Pa-MAP1.9 acts within the cell, while Pa-MAP2 acts via membrane lysis. In conclusion, polyalanine Pa-MAP1.9 and Pa-MAP2 presented activity against bloodstream forms of T. b. gambiense, thus encouraging further studies on the application of these peptides as a treatment for sleeping sickness.

Mapping Salivary Proteases in Sjögren's Syndrome Patients Reveals Overexpression of Dipeptidyl Peptidase-4/CD26.

Sjögren's Syndrome (SS) is an autoimmune exocrinopathy characterized by the progressive damage of salivary and lacrimal glands associated with lymphocytic infiltration. Identifying new non-invasive biomarkers for SS diagnosis remains a challenge, and alterations in saliva composition reported in patients turn this fluid into a source of potential biomarkers. Among these, proteases are promising candidates since they are involved in several key physio-pathological processes. This study evaluated differentially expressed proteases in SS individuals' saliva using synthetic fluorogenic substrates, zymography, ELISA, and proteomic approaches. Here we reported, for the first time, increased activity of the serine protease dipeptidyl peptidase-4/CD26 (DPP4/CD26) in pSS saliva, the expression level of which was corroborated by ELISA assay. Gelatin zymograms showed that metalloproteinase proteolytic band profiles differed significantly in intensity between control and SS groups. Focusing on matrix metalloproteinase-9 (MMP9) expression, an increased tendency in pSS saliva (p = 0.0527) was observed compared to the control group. Samples of control, pSS, and sSS were analyzed by mass spectrometry to reveal a general panorama of proteases in saliva. Forty-eight protein groups of proteases were identified, among which were the serine proteases cathepsin G (CTSG), neutrophil elastase (ELANE), myeloblastin (PRTN3), MMP9 and several protease inhibitors. This work paves the way for proteases to be explored in the future as biomarkers, emphasizing DPP4 by its association in several autoimmune and inflammatory diseases. Besides its proteolytic role, DPP4/CD26 acts as a cell surface receptor, signal transduction mediator, adhesion and costimulatory protein involved in T lymphocytes activation.

Comparative Two-Dimensional Gel Electrophoresis of Trypanosoma cruzi Mammalian-Stage Forms in an Alkaline pH Range.

It is estimated that several million people are currently infected worldwide by the protozoan parasite, Trypanosoma cruzi, which causes Chagas disease. After mammalian host infection, a fundamental event is the differentiation from infective trypomastigotes into replicative amastigotes (amastigogenesis) inside host-cells. To unravel the particularities of both forms, it is essential to identify molecules presented in each form. Since T. cruzi gene expression regulation occurs mainly at posttranscriptional level, a proteomic approach is appropriate. Due to intrinsic difficulties with performing 2-DE in the alkaline pH range, there are no reports on 2-DE-based comparative proteome analysis of T. cruzi mammalianstage forms that focus on alkaline polypeptides. Here, we performed a comparative proteome analysis between tissue culture- derived trypomastigotes and extracellular amastigote-like cells using conditions optimized for the 6-11 pH range followed by identification by MALDI-TOF/TOF technology. The alkaline 2-DE maps from both forms show that proteins with a pI above 7.0 were not underrepresented (= 65% of proteins detected). Moreover the differences in protein expression between the Human-hosted T. cruzi forms corroborated previous proteomic studies and corresponded to their biological traits.

Quantitative proteomic and phosphoproteomic analysis of Trypanosoma cruzi amastigogenesis.

Chagas disease is a tropical neglected disease endemic in Latin America caused by the protozoan Trypanosoma cruzi. The parasite has four major life stages: epimastigote, metacyclic trypomastigote, bloodstream trypomastigote, and amastigote. The differentiation from infective trypomastigotes into replicative amastigotes, called amastigogenesis, takes place in vivo inside mammalian host cells after a period of incubation in an acidic phagolysosome. This differentiation process can be mimicked in vitro by incubating tissue-culture-derived trypomastigotes in acidic DMEM. Here we used this well-established differentiation protocol to perform a comprehensive quantitative proteomic and phosphoproteomic analysis of T. cruzi amastigogenesis. Samples from fully differentiated forms and two biologically relevant intermediate time points were Lys-C/trypsin digested, iTRAQ-labeled, and multiplexed. Subsequently, phosphopeptides were enriched using a TiO2 matrix. Non-phosphorylated peptides were fractionated via hydrophilic interaction liquid chromatography prior to LC-MS/MS analysis. LC-MS/MS and bioinformatics procedures were used for protein and phosphopeptide quantitation, identification, and phosphorylation site assignment. We were able to identify regulated proteins and pathways involved in coordinating amastigogenesis. We also observed that a significant proportion of the regulated proteins were membrane proteins. Modulated phosphorylation events coordinated by protein kinases and phosphatases that are part of the signaling cascade induced by incubation in acidic medium were also evinced. To our knowledge, this work is the most comprehensive quantitative proteomics study of T. cruzi amastigogenesis, and these data will serve as a trustworthy basis for future studies, and possibly for new potential drug targets.

Prolyl oligopeptidase of Trypanosoma brucei hydrolyzes native collagen, peptide hormones and is active in the plasma of infected mice.

Proteases play important roles in many biological processes of parasites, including their host interactions. In sleeping sickness, Trypanosoma brucei proteases released into the host bloodstream could hydrolyze host factors, such as hormones, contributing to the development of the disease's symptoms. In this study, we present the identification of the T. brucei prolyl oligopeptidase gene (poptb) and the characterization of its corresponding enzyme, POP Tb. Secondary structure predictions of POP Tb show a structural composition highly similar to other POPs. Recombinant POP Tb produced in E. coli was active and highly sensitive to inhibitors of Trypanosoma cruzi POP Tc80. These inhibitors, which prevent T. cruzi entry into non-phagocytic cells, arrested growth of the T. brucei bloodstream form in a dose-dependent manner. POP Tb hydrolyzes peptide hormones containing Pro or Ala at the P1 position at a slightly alkaline pH, and also cleaves type I collagen in vitro and native collagen present in rat mesentery. Furthermore, POP Tb is released into the bloodstream of T. brucei infected mice where it remains active. These data suggest that POP Tb might contribute to the pathogenesis of sleeping sickness.

Photochemical inactivation with amotosalen and long-wavelength ultraviolet light of Plasmodium and Babesia in platelet and plasma components.

BACKGROUND: Transfusion-transmitted cases of malaria and babesiosis have been well documented. Current efforts to screen out contaminated blood products result in component wastage due to the lack of specific detection methods while donor deferral does not always guarantee safe blood products. This study evaluated the efficacy of a photochemical treatment (PCT) method with amotosalen and long-wavelength ultraviolet light (UVA) to inactivate these agents in red blood cells (RBCs) contaminating platelet (PLT) and plasma components. STUDY DESIGN AND METHODS: Plasmodium falciparum- and Babesia microti-contaminated RBCs seeded into PLT and plasma components were treated with 150 micromol per L amotosalen and 3 J per cm2 UVA. The viability of both pathogens before and after treatment was measured with infectivity assays. Treatment with 150 micromol per L amotosalen and 1 J per cm2 UVA was used to assess the robustness of the PCT system. RESULTS: No viable B. microti was detected in PLTs or plasma after treatment with 150 mol per L amotosalen and 3 J per cm2 UVA, demonstrating a mean inactivation of greater than 5.3 log in PLTs and greater than 5.3 log in plasma. After the same treatment, viable P. falciparum was either absent or below the limit of quantification in three of four replicate experiments both in PLTs and in plasma demonstrating a mean inactivation of at least 6.0 log in PLTs and at least 6.9 log in plasma. Reducing UVA dose to 1 J per cm2 did not significantly affect the level of inactivation. CONCLUSION: P. falciparum and B. microti were highly sensitive to inactivation by PCT. Pathogen inactivation approaches could reduce the risk of transfusion-transmitted parasitic infections and avoid unnecessary donor exclusions.