Lipase Precursor-Like Protein Promotes Miltefosine Tolerance in Leishmania donovani by Enhancing Parasite Infectivity and Eliciting Anti-inflammatory Responses in Host Macrophages

Non-Vesicular Lipid Transport Machinery in Leishmania donovani: Functional Implications in Host-Parasite Interaction

Eukaryotic cells have distinct membrane-enclosed organelles, each with a unique biochemical signature and specialized function. The unique identity of each organelle is greatly governed by the asymmetric distribution and regulated intracellular movement of two important biomolecules, lipids, and proteins. Non-vesicular lipid transport mediated by lipid-transfer proteins (LTPs) plays essential roles in intra-cellular lipid trafficking and cellular lipid homeostasis, while vesicular transport regulates protein trafficking. A comparative analysis of non-vesicular lipid transport machinery in protists could enhance our understanding of parasitism and basis of eukaryotic evolution. Leishmania donovani, the trypanosomatid parasite, greatly depends on receptor-ligand mediated signalling pathways for cellular differentiation, nutrient uptake, secretion of virulence factors, and pathogenesis. Lipids, despite being important signalling molecules, have intracellular transport mechanisms that are largely unexplored in L. donovani. We have identified a repertoire of sixteen (16) potential lipid transfer protein (LTP) homologs based on a domain-based search on TriTrypDB coupled with bioinformatics analyses, which signifies the presence of well-organized lipid transport machinery in this parasite. We emphasized here their evolutionary uniqueness and conservation and discussed their potential implications for parasite biology with regards to future therapeutic targets against visceral leishmaniasis.

3'Nucleotidase/nuclease is required for Leishmania infantum clinical isolate susceptibility to miltefosine

BACKGROUND

Miltefosine treatment failure in visceral leishmaniasis in Brazil has been associated with deletion of the miltefosine susceptibility locus (MSL) in Leishmania infantum. The MSL comprises four genes, 3'-nucleotidase/nucleases (NUC1 and NUC2); helicase-like protein (HLP); and 3,2-trans-enoyl-CoA isomerase (TEI).

METHODS

In this study CRISPR-Cas9 was used to either epitope tag or delete NUC1, NUC2, HLP and TEI, to investigate their role in miltefosine resistance mechanisms. Additionally, miltefosine transporter genes and miltefosine-mediated reactive oxygen species homeostasis were assessed in 26 L. infantum clinical isolates. A comparative lipidomic analysis was also performed to investigate the molecular basis of miltefosine resistance.

FINDINGS

Deletion of both NUC1, NUC2 from the MSL was associated with a significant decrease in miltefosine susceptibility, which was restored after re-expression. Metabolomic analysis of parasites lacking the MSL or NUC1 and NUC2 identified an increase in the parasite lipid content, including ergosterol; these lipids may contribute to miltefosine resistance by binding the drug in the membrane. Parasites lacking the MSL are more resistant to lipid metabolism perturbation caused by miltefosine and NUC1 and NUC2 are involved in this pathway. Additionally, L. infantum parasites lacking the MSL isolated from patients who relapsed after miltefosine treatment were found to modulate nitric oxide accumulation in host macrophages.

INTERPRETATION

Altogether, these data indicate that multifactorial mechanisms are involved in natural resistance to miltefosine in L. infantum and that the absence of the 3'nucleotidase/nuclease genes NUC1 and NUC2 contributes to the phenotype.

FUNDING

MRC GCRF and FAPES.

Leishmania donovani chaperonin TCP1γ subunit protects miltefosine induced oxidative damage

T-complex protein-1 (TCP1) is a chaperonin protein known to fold various proteins like actin and tubulin. In Leishmania donovani only one subunit of TCP1 that is gamma subunit (LdTCP1γ) has been functionally characterized. It not only performs ATP dependent protein folding but is also essential for survival and virulence. The present work demonstrates that LdTCP1γ also has a role in miltefosine resistance. Overexpression of LdTCP1γ in L. donovani promastigotes results in decreased sensitivity of parasites towards miltefosine, while single-allele replacement mutants exhibited increased sensitivity as compared to wild-type promastigotes. This response was specific to miltefosine with no cross-resistance to other drugs. The LdTCP1γ-mediated drug resistance was directly related to miltefosine-induced apoptotic death of the parasite, as was evidenced by 2 to 3-fold decrease in cell death parameters in overexpressing cells and >2-fold increase in single-allele replacement mutants. Further, deciphering the mechanism revealed that resistance of overexpressing cells was associated with efficient ROS neutralization due to increased levels of thiols and upregulation of cytosolic tryparedoxin peroxidase (cTxnPx). Further, modulation of LdTCP1γ expression in parasite also modulates the levels of proinflammatory cytokine (TNF-α) and anti-inflammatory cytokine (IL-10) of the host macrophages. The study provides evidence for the involvement of a chaperonin protein LdTCP1γ in the protection against miltefosine induced oxidative damage and reveals the fundamental role of LdTCP1γ in parasite biology.

Involvement of lipids from Leishmania braziliensis promastigotes and amastigotes in macrophage activation

Leishmania are obligate protozoan parasites responsible for substantial public health problems in tropical and subtropical regions around the world, with L. braziliensis being one of the causative agents of American Tegumentary Leishmaniasis. Macrophages, fundamental cells in the innate inflammatory response against Leishmania, constitute a heterogeneous group with multiple activation phenotypes and functions. The outcome of this infection depends largely on the activation status of macrophages, the first line of mammalian defense and the major target cells for parasite replication. The importance of lipids, the major components of cell membranes, goes beyond their basic structural functions. Lipid bioactive molecules have been described in Leishmania spp., and in the recent years the knowledge about the biological relevance of lipids in particular and their relationship with the immune response is expanding. The present work analyzes the biological effects of L. braziliensis lipids from lysed promastigotes (PRO) to mimic rapid modulatory processes that could occur in the initial steps of infection or the effects of lipids from lysed and incubated promastigotes (PROinc), simulating the parasite lipid degradation processes triggered after parasite lysis that might occur in the mammalian host. To perform these studies, lipid profiles of PRO and PROinc were compared with lipids from amastigotes under similar conditions (AMA and AMAinc), and the effect of these lipid extracts were analyzed on the induction of an inflammatory response in murine peritoneal macrophages: LB induction, COX-2, iNOS and Arginase expression, TNF-α, IL-10 and NO production, Arginase activity and M1/M2 markers mRNA induction.

Cellular localization, cloning and expression of Leishmania braziliensis Phospholipase A1

Leishmaniasis is caused by several species of protozoan parasites of the genus Leishmania and represents an important global health problem. Leishmania braziliensis in particular is responsible of cutaneous and mucocutaneous forms of this parasitosis, with prevalence in Latin America. In the present work, we describe in L. braziliensis promastigotes and amastigotes the presence of a Phospholipase A₁ (PLA₁) activity, an enzyme that catalyses extensive deacylation of phospholipids like phosphatidylcholine. In order to deepen the knowledge about L. braziliensis PLA₁, the cloning and expression of the gene that codifies for this enzyme was carried out in a baculovirus expression system with the obtaintion of a purified recombinant protein that displayed PLA₁ activity. Given that this is the first molecular and functional protein characterization of a PLA₁ in the Leishmania genus, we also performed a phylogenetic analysis of this gene throughout 12 species whose genome sequences were available. The results presented here will contribute to increase the knowledge about trypanosome phospholipases, which could be novel and valuable as potential targets to fight neglected diseases like Leishmaniasis.