Deciphering the role of UBA-like domains in intraflagellar distribution and functions of myosin XXI in Leishmania

Ubiquitin and ubiquitin-like conjugation systems in trypanosomatids

In eukaryotic cells, reversible attachment of ubiquitin and ubiquitin-like modifiers (Ubls) to specific target proteins is conducted by multicomponent systems whose collective actions control protein fate and cell behaviour in precise but complex ways. In trypanosomatids, attachment of ubiquitin and Ubls to target proteins regulates the cell cycle, endocytosis, protein sorting and degradation, autophagy and various aspects of infection and stress responses. The extent of these systems in trypanosomatids has been surveyed in recent reports, while in Leishmania mexicana, essential roles have been defined for many ubiquitin-system genes in deletion mutagenesis and life-cycle phenotyping campaigns. The first steps to elucidate the pathways of ubiquitin transfer among the ubiquitination components and to define the acceptor substrates and the downstream deubiquitinases are now being taken.

Effects of negative air ions (NAIs) on Leishmania major: A novel tool for treatment of zoonotic cutaneous leishmaniasis (ZCL)

Background

Cutaneous leishmaniasis (CL) is a Neglected Tropical Disease (NTD) that causes high morbidity in the tropics and sub-tropics. Despite the remarkable advancements in the treatment of CL, the available therapeutics are far from ideal and also cause serious adverse side effects. Negative air ions (NAIs) generators are widely available for domestic and industrial uses. Several studies have reported on positive effects of NAIs therapy on human health as a non-pharmaceutical treatment for respiratory disease, allergy, or stress-related health conditions, including infectious diseases. To our knowledge, no studies have examined the effectiveness of the NAIs therapy against Leishmania parasites. The aims of this study were to investigate the effect of NAIs therapy on Leishmania major (L. major) the causative agent of CL in in vitro and in a murine model.

Methodology/Principal findings

In vitro anti-leishmanial effects of NAIs therapy were measured by parasitological methods. NAIs therapy was assessed in vivo in L. major infected BALB/c mice by measuring the footpad (FP) lesion size and parasite load using metric caliper tool and qPCR, respectively. Immune responses in treated and non-treated mice were assessed by measuring the levels of IFN-γ, IL-4, NO and arginase activity. In vitro NAIs therapy significantly decreased the viability of Leishmania promastigotes and of amastigotes cultured in macrophages, but did not affect the host cells. NAIs therapy of L. major infected BALB/c mice resulted in reduced FP lesion size, diminished parasite burden, and importantly decreased induction of IL-4 and arginase activity in the presence of NAIs. In contrast IFN-γ and NO levels were significantly enhanced. NAIs therapy significantly diminished the progression of disease compared to the control group, but was less effective than amphotericin B treatment.

Conclusions

Our study shows that NAIs treatment was effective in vitro and in Leishmania-infected mice, elicited a T-helper 1 (Th1) response and increased efficient cellular immunity, resulting in a diminished parasite load. Therefore, NAIs therapy can be considered as a useful and safe tool that can contribute to clearing L. major infections without inducing toxicity in host cells. The applications and mechanisms of NAIs therapy warrant further investigation especially in humans suffering from CL.

Unraveling of interacting protein network of chaperonin TCP1 gamma subunit of Leishmania donovani

T-complex polypeptide-1 (TCP1) is a group II chaperonin that folds various cellular proteins. About 10% of cytosolic proteins in yeast have been shown to flux through the TCP1 protein complex indicating that it interacts and folds a plethora of substrate proteins that perform essential functions. In Leishmania donovani, the gamma subunit of TCP1 (LdTCP1γ) has been shown to form a homo-oligomeric complex and exhibited ATP-dependent protein folding activity. LdTCP1γ is essential for the growth and infectivity of the parasite. The interacting partners of L. donovani TCP1γ, involved in many cellular processes, are far from being understood. In this study, we utilized co-immunoprecipitation assay coupled with liquid chromatography-mass spectrometry (LC-MS) to unravel protein-protein interaction (PPI) networks of LdTCP1γ in the L. donovani parasite. Label-free quantification (LFQ) proteomic analysis revealed 719 interacting partners of LdTCP1γ. String analysis showed that LdTCP1γ interacts with all subunits of TCP1 complex as well as other proteins belonging to pathways like metabolic process, ribosome, protein folding, sorting, and degradation. Trypanothione reductase, identified as one of the interacting partners, is refolded by LdTCP1γ. In addition, the differential expression of LdTCP1γ modulates the trypanothione reductase activity in L. donovani parasite. The study provides novel insight into the role of LdTCP1γ that will pave the way to better understand parasite biology by identifying the interacting partners of this chaperonin.

Emerging Functions of Actins and Actin Binding Proteins in Trypanosomatids

Actin is the major protein constituent of the cytoskeleton that performs wide range of cellular functions. It exists in monomeric and filamentous forms, dynamics of which is regulated by a large repertoire of actin binding proteins. However, not much was known about existence of these proteins in trypanosomatids, till the genome sequence data of three important organisms of this class, viz. Trypanosoma brucei, Trypanosoma cruzi and Leishmania major, became available. Here, we have reviewed most of the findings reported to date on the intracellular distribution, structure and functions of these proteins and based on them, we have hypothesized some of their functions. The major findings are as follows: (1) All the three organisms encode at least a set of ten actin binding proteins (profilin, twinfilin, ADF/cofilin, CAP/srv2, CAPz, coronin, two myosins, two formins) and one isoform of actin, except that T. cruzi encodes for three formins and several myosins along with four actins. (2) Actin 1 and a few actin binding proteins (ADF/cofilin, profilin, twinfilin, coronin and myosin13 in L. donovani; ADF/cofilin, profilin and myosin1 in T. brucei; profilin and myosin-F in T.cruzi) have been identified and characterized. (3) In all the three organisms, actin cytoskeleton has been shown to regulate endocytosis and intracellular trafficking. (4) Leishmania actin1 has been the most characterized protein among trypanosomatid actins. (5) This protein is localized to the cytoplasm as well as in the flagellum, nucleus and kinetoplast, and in vitro, it binds to DNA and displays scDNA relaxing and kDNA nicking activities. (6) The pure protein prefers to form bundles instead of thin filaments, and does not bind DNase1 or phalloidin. (7) Myosin13, myosin1 and myosin-F regulate endocytosis and intracellular trafficking, respectively, in Leishmania, T. brucei and T. cruzi. (8) Actin-dependent myosin13 motor is involved in dynamics and assembly of Leishmania flagellum. (9) Leishmania twinfilin localizes mostly to the nucleolus and coordinates karyokinesis by effecting splindle elongation and DNA synthesis. (10) Leishmania coronin binds and promotes actin filament formation and exists in tetrameric form rather than trimeric form, like other coronins. (11) Trypanosomatid profilins are essential for survival of all the three parasites.