Overlooked post-translational modifications of proteins in Plasmodium falciparum: N- and O-glycosylation -- a review.

Human malignant malaria is caused by Plasmodium falciparum and accounts for almost 900,000 deaths per year, the majority of which are children and pregnant women in developing countries. There has been significant effort to understand the biology of P. falciparum and its interactions with the host. However, these studies are hindered because several aspects of parasite biology remain controversial, such as N- and O-glycosylation. This review describes work that has been done to elucidate protein glycosylation in P. falciparum and it focuses on describing biochemical evidence for N- and O-glycosylation. Although there has been significant work in this field, these aspects of parasite biochemistry need to be explored further.

Altered composition and functional profile of high-density lipoprotein in leprosy patients.

The changes in host lipid metabolism during leprosy have been correlated to fatty acid alterations in serum and with high-density lipoprotein (HDL) dysfunctionality. This is most evident in multibacillary leprosy patients (Mb), who present an accumulation of host lipids in Schwann cells and macrophages. This accumulation in host peripheral tissues should be withdrawn by HDL, but it is unclear why this lipoprotein from Mb patients loses this function. To investigate HDL metabolism changes during the course of leprosy, HDL composition and functionality of Mb, Pb patients (paucibacillary) pre- or post-multidrug therapy (MDT) and HC (healthy controls) were analyzed. Mb pre-MDT patients presented lower levels of HDL-cholesterol compared to HC. Moreover, Ultra Performance Liquid Chromatography-Mass Spectrometry lipidomics of HDL showed an altered lipid profile of Mb pre-MDT compared to HC and Pb patients. In functional tests, HDL from Mb pre-MDT patients showed impaired anti-inflammatory and anti-oxidative stress activities and a lower cholesterol acceptor capacity compared to other groups. Mb pre-MDT showed lower concentrations of ApoA-I (apolipoprotein A-I), the major HDL protein, when compared to HC, with a post-MDT recovery. Changes in ApoA-I expression could also be observed in M. leprae-infected hepatic cells. The presence of bacilli in the liver of a Mb patient, along with cell damage, indicated hepatic involvement during leprosy, which may reflect on ApoA-I expression. Together, altered compositional and functional profiles observed on HDL of Mb patients can explain metabolic and physiological changes observed in Mb leprosy, contributing to a better understanding of its pathogenesis.

MALDI imaging reveals lipid changes in the skin of leprosy patients before and after multidrug therapy (MDT).

Leprosy still represents a health problem in several countries. Affecting skin and peripheral nerves, it may lead to permanent disabilities. Disturbances on skin lipid metabolism in leprosy were already observed; however, the localization and distribution of lipids could not be accessed. The role of lipids on infectious disease has been fully addressed only recently, as they directly influence immune response. Matrix-assisted laser desorption/ionization imaging mass spectrometry provides a powerful tool to localize and identify lipids in tissues. The aim of this work was to study and compare the changes in lipid distribution of skin biopsies taken from leprosy patients before and after multidrug therapy (MDT). Different species of phosphatidic acid, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, sphingomyelin and phosphatidylcholine were detected. Differences in skin lipid signal intensities, as well as in their localization, were observed before and after MDT in every patient. In general, lipid distribution in the skin after MDT had a pattern similar to control skin samples, where most of the lipids were located in the upper part of the dermis and epidermis. This study opens paths to a better understanding of lipid functions in leprosy pathogenesis and immune response.

Identification and functional analysis of Trypanosoma cruzi genes that encode proteins of the glycosylphosphatidylinositol biosynthetic pathway.

BACKGROUND: Trypanosoma cruzi is a protist parasite that causes Chagas disease. Several proteins that are essential for parasite virulence and involved in host immune responses are anchored to the membrane through glycosylphosphatidylinositol (GPI) molecules. In addition, T. cruzi GPI anchors have immunostimulatory activities, including the ability to stimulate the synthesis of cytokines by innate immune cells. Therefore, T. cruzi genes related to GPI anchor biosynthesis constitute potential new targets for the development of better therapies against Chagas disease. METHODOLOGY/PRINCIPAL FINDINGS: In silico analysis of the T. cruzi genome resulted in the identification of 18 genes encoding proteins of the GPI biosynthetic pathway as well as the inositolphosphorylceramide (IPC) synthase gene. Expression of GFP fusions of some of these proteins in T. cruzi epimastigotes showed that they localize in the endoplasmic reticulum (ER). Expression analyses of two genes indicated that they are constitutively expressed in all stages of the parasite life cycle. T. cruzi genes TcDPM1, TcGPI10 and TcGPI12 complement conditional yeast mutants in GPI biosynthesis. Attempts to generate T. cruzi knockouts for three genes were unsuccessful, suggesting that GPI may be an essential component of the parasite. Regarding TcGPI8, which encodes the catalytic subunit of the transamidase complex, although we were able to generate single allele knockout mutants, attempts to disrupt both alleles failed, resulting instead in parasites that have undergone genomic recombination and maintained at least one active copy of the gene. CONCLUSIONS/SIGNIFICANCE: Analyses of T. cruzi sequences encoding components of the GPI biosynthetic pathway indicated that they are essential genes involved in key aspects of host-parasite interactions. Complementation assays of yeast mutants with these T. cruzi genes resulted in yeast cell lines that can now be employed in high throughput screenings of drugs against this parasite.

Metabonomics reveals drastic changes in anti-inflammatory/pro-resolving polyunsaturated fatty acids-derived lipid mediators in leprosy disease.

Despite considerable efforts over the last decades, our understanding of leprosy pathogenesis remains limited. The complex interplay between pathogens and hosts has profound effects on host metabolism. To explore the metabolic perturbations associated with leprosy, we analyzed the serum metabolome of leprosy patients. Samples collected from lepromatous and tuberculoid patients before and immediately after the conclusion of multidrug therapy (MDT) were subjected to high-throughput metabolic profiling. Our results show marked metabolic alterations during leprosy that subside at the conclusion of MDT. Pathways showing the highest modulation were related to polyunsaturated fatty acid (PUFA) metabolism, with emphasis on anti-inflammatory, pro-resolving omega-3 fatty acids. These results were confirmed by eicosanoid measurements through enzyme-linked immunoassays. Corroborating the repertoire of metabolites altered in sera, metabonomic analysis of skin specimens revealed alterations in the levels of lipids derived from lipase activity, including PUFAs, suggesting a high lipid turnover in highly-infected lesions. Our data suggest that omega-6 and omega-3, PUFA-derived, pro-resolving lipid mediators contribute to reduced tissue damage irrespectively of pathogen burden during leprosy disease. Our results demonstrate the utility of a comprehensive metabonomic approach for identifying potential contributors to disease pathology that may facilitate the development of more targeted treatments for leprosy and other inflammatory diseases.

Overlooked post-translational modifications of proteins in Plasmodium falciparum: N- and O-glycosylation - A Review

Human malignant malaria is caused by Plasmodium falciparum and accounts for almost 900,000 deaths per year, the majority of which are children and pregnant women in developing countries. There has been significant effort to understand the biology of P. falciparum and its interactions with the host. However, these studies are hindered because several aspects of parasite biology remain controversial, such as N- and O-glycosylation. This review describes work that has been done to elucidate protein glycosylation in P. falciparum and it focuses on describing biochemical evidence for N- and O-glycosylation. Although there has been significant work in this field, these aspects of parasite biochemistry need to be explored further.