Molecular Chaperones of Leishmania: Central Players in Many Stress-Related and -Unrelated Physiological Processes

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.

Novel Strategy for In Vitro Validation of Babesia orientalis Heat Shock Proteins Chaperone Activity and Thermostability

BACKGROUND

Babesia orientalis is an intra-erythrocytic protozoan parasite that causes babesiosis in water buffalo. The genome of B. orientalis has been reported and various genes have been accurately annotated, including heat shock proteins (HSP). Three B. orientalis HSPs (HSP90, HSP70 and HSP20) have been previously identified as potential antigenic targets. Here, a new validation strategy for the chaperone activities and cell protection characteristics of the three HSPs was developed in vitro.

METHODS

BoHSP20, BoHSP70 and BoHSP90B were amplified from cDNA, followed by cloning them into the pEGFP-N1 vector and transfecting the vector plasmid separately into 293T and Hela mammalian cells. Their expression and localization were determined by fluorescence microscopy. The biological functions and protein stability were testified through an analysis of the fluorescence intensity duration. Their role in the protection of cell viability from heat-shock treatments was examined by MTT assay (cell proliferation assay based on thiazolyl blue tetrazolium bromide).

RESULTS

Fusion proteins pEGFP-N1-BoHSP20, pEGFP-N1-BoHSP70, and pEGFP-N1-BoHSP90B (pBoHSPs: pBoHSP20; pBoHSP70 and pBoHSP90B) were identified as 47 kDa/97 kDa/118 kDa with a 27 kDa GFP tag, respectively. Prolonged fluorescent protein half-time was observed specifically in pBoHSPs under heat shock treatment at 55 °C, and BoHSP20 showed relatively better thermotolerance than BoHSP70 and BoHSP90B. Significant difference was found between pBoHSPs and controls in the cell survival curve after 2 h of 45 °C heat shock.

CONCLUSION

Significant biological properties of heat stress-associated genes of B. orientalis were identified in eukaryote by a new strategy. Fusion proteins pBoHSP20, pBoHSP70 and pBoHSP90B showed good chaperone activity and thermo-stability in this study, implying that BoHSPs played a key role in protecting B. orientalis against heat-stress environment during parasite life cycle. In conclusion, the in vitro model explored in this study provides a new way to investigate the biological functions of B. orientalis proteins during the host-parasite interaction.

Gene cloning and characterization of a novel recombinant 40-kDa heat shock protein from Mesobacillus persicus B48

The present study reports the recognition and characterization of the gene encoding the co-chaperone DnaJ in the halophilic strain Mesobacillus persicus B48. The new extracted gene was sequenced and cloned in E. coli, followed by protein purification using a C-terminal His-tag. The stability and function of the recombinant DnaJ protein under salt and pH stress conditions were evaluated. SDS-PAGE revealed a band on nearly 40-kDa region. The homology model structure of new DnaJ demonstrated 56% similarity to the same protein from Streptococcus pneumonia. Fluorescence spectra indicated several hydrophobic residues located on the protein surface, which is consistent with the misfolded polypeptide recognition function of DnaJ. Spectroscopic results showed 56% higher carbonic anhydrase activity in the presence of the recombinant DnaJ homolog compared to its absence. In addition, salt resistance experiments showed that the survival of recombinant E. coli+DnaJ was 2.1 times more than control cells in 0.5 M NaCl. Furthermore, the number of recombinant E. coli BL21+DnaJ colonies was 7.7 times that of the control colonies in pH 8.5. Based on the results, DnaJ from the M. persicus can potentially be employed for improving the functional features of enzymes and other proteins in various applications.

The endoplasmic reticulum of trypanosomatids: An unrevealed road for chemotherapy

The endoplasmic reticulum (ER) of higher eukaryotic cells forms an intricate membranous network that serves as the main processing facility for folding and assembling of secreted and membrane proteins. The ER is a highly dynamic organelle that interacts with other intracellular structures, as well as endosymbiotic pathogenic and non-pathogenic microorganisms. A strict ER quality control (ERQC) must work to ensure that proteins entering the ER are folded and processed correctly. Unfolded or misfolded proteins are usually identified, selected, and addressed to Endoplasmic Reticulum-Associated Degradation (ERAD) complex. Conversely, when there is a large demand for secreted proteins or ER imbalance, the accumulation of unfolded or misfolded proteins activates the Unfold Protein Response (UPR) to restore the ER homeostasis or, in the case of persistent ER stress, induces the cell death. Pathogenic trypanosomatids, such as Trypanosoma cruzi, Trypanosoma brucei and Leishmania spp are the etiological agents of important neglected diseases. These protozoans have a complex life cycle alternating between vertebrate and invertebrate hosts. The ER of trypanosomatids, like those found in higher eukaryotes, is also specialized for secretion, and depends on the ERAD and non-canonical UPR to deal with the ER stress. Here, we reviewed the basic aspects of ER biology, organization, and quality control in trypanosomatids. We also focused on the unusual way by which T. cruzi, T. brucei, and Leishmania spp. respond to ER stress, emphasizing how these parasites' ER-unrevealed roads might be an attractive target for chemotherapy.

In silico analysis of the HSP90 chaperone system from the African trypanosome, Trypanosoma brucei

African trypanosomiasis is a neglected tropical disease caused by Trypanosoma brucei (T. brucei) and spread by the tsetse fly in sub-Saharan Africa. The trypanosome relies on heat shock proteins for survival in the insect vector and mammalian host. Heat shock protein 90 (HSP90) plays a crucial role in the stress response at the cellular level. Inhibition of its interactions with chaperones and co-chaperones is being explored as a potential therapeutic target for numerous diseases. This study provides an in silico overview of HSP90 and its co-chaperones in both T. brucei brucei and T. brucei gambiense in relation to human and other trypanosomal species, including non-parasitic Bodo saltans and the insect infecting Crithidia fasciculata. A structural analysis of T. brucei HSP90 revealed differences in the orientation of the linker and C-terminal domain in comparison to human HSP90. Phylogenetic analysis displayed the T. brucei HSP90 proteins clustering into three distinct groups based on subcellular localizations, namely, cytosol, mitochondria, and endoplasmic reticulum. Syntenic analysis of cytosolic HSP90 genes revealed that T. b. brucei encoded for 10 tandem copies, while T. b. gambiense encoded for three tandem copies; Leishmania major (L. major) had the highest gene copy number with 17 tandem copies. The updated information on HSP90 from recently published proteomics on T. brucei was examined for different life cycle stages and subcellular localizations. The results show a difference between T. b. brucei and T. b. gambiense with T. b. brucei encoding a total of twelve putative HSP90 genes, while T. b. gambiense encodes five HSP90 genes. Eighteen putative co-chaperones were identified with one notable absence being cell division cycle 37 (Cdc37). These results provide an updated framework on approaching HSP90 and its interactions as drug targets in the African trypanosome.

Identification of protein biomarkers of attenuation and immunogenicity of centrin or p27 gene deleted live vaccine candidates of Leishmania against visceral leishmaniasis

Currently, no licensed vaccine is available for human visceral leishmaniasis (VL), a fatal disease caused by the protozoan parasite Leishmania donovani. Two of our live attenuated L. donovani vaccine candidates, either deleted for Centrin1 (LdCen1^-/-) or p27 gene (Ldp27^-/-), that display reduced growth in macrophages were studied to be safe, immunogenic and protective against VL in various animal models. This report involves the identification of differentially expressed proteins, their related pathways and its underlying mechanism in the intracellular stage of these parasites, using Isobaric Tags for Relative and Absolute Quantitation (iTRAQ) methods. Out of 50-60 proteins, found to be differentially expressed in these mutant parasites, 36 were found to be common in both the parasites. Such proteins mainly belong to the functional categories viz. metabolic enzymes, chaperones and stress proteins, proteins involved in translation, processing and transport and proteins involved in nucleic acid processing. Proteins known to be host protective, like Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), cytochrome c, calreticulin and those responsible for inducing immune response, namely tubulins, DEAD box RNA helicases, HSP70 and tryparedoxin, have been detected to be modulated in these parasites. Such proteins could be predicted as biomarkers, with further scope of study for their role in growth attenuation. SIGNIFICANCE: This study aims at predicting proteomic biomarkers of Leishmania parasite growth attenuation, that have immunomodulatory role in the disease leishmaniasis. Advanced studies could be helpful in establishing the role of these identified proteins in parasitic virulence and to predict the host interaction at molecular level. Also, these proteins could be exploited as attenuation markers during the development of genetically modified live attenuated parasites as vaccine candidates. These could be cross validated in varied species of Leishmania and other tyrpanosomatids for similar response towards identifying them as universal biomarkers of attenuation.

Exploring direct and indirect targets of current antileishmanial drugs using a novel thermal proteomics profiling approach

Visceral leishmaniasis (VL), caused by Leishmania infantum, is an oft-fatal neglected tropical disease. In the absence of an effective vaccine, the control of leishmaniasis relies exclusively on chemotherapy. Due to the lack of established molecular/genetic markers denoting parasite resistance, clinical treatment failure is often used as an indicator. Antimony-based drugs have been the standard antileishmanial treatment for more than seven decades, leading to major drug resistance in certain regions. Likewise, drug resistance to miltefosine and amphotericin B continues to spread at alarming rates. In consequence, innovative approaches are needed to accelerate the identification of antimicrobial drug targets and resistance mechanisms. To this end, we have implemented a novel approach based on thermal proteome profiling (TPP) to further characterize the mode of action of antileishmanials antimony, miltefosine and amphotericin B, as well as to better understand the mechanisms of drug resistance deployed by Leishmania. Proteins become more resistant to heat-induced denaturation when complexed with a ligand. In this way, we used multiplexed quantitative mass spectrometry-based proteomics to monitor the melting profile of thousands of expressed soluble proteins in WT, antimony-resistant, miltefosine-resistant, and amphotericin B-resistant L. infantum parasites, in the presence (or absence) of the above-mentioned drugs. Bioinformatics analyses were performed, including data normalization, melting profile fitting, and identification of proteins that underwent changes (fold change > 4) caused by complexation with a drug. With this unique approach, we were able to narrow down the regions of the L. infantum proteome that interact with antimony, miltefosine, and amphotericin B; validating previously-identified and unveiling novel drug targets. Moreover, analyses revealed candidate proteins potentially involved in drug resistance. Interestingly, we detected thermal proximity coaggregation for several proteins belonging to the same metabolic pathway (i.e., tryparedoxin peroxidase and aspartate aminotransferase in proteins exposed to antimony), highlighting the importance of these pathways. Collectively, our results could serve as a jumping-off point for the future development of innovative diagnostic tools for the detection and evaluation of antimicrobial-resistant Leishmania populations, as well as open the door for new on-target therapies.

Virulence factors of Leishmania parasite: Their paramount importance in unraveling novel vaccine candidates and therapeutic targets

Leishmaniasis is a neglected tropical disease and remains a global concern for healthcare. It is caused by an opportunistic protozoan parasite belonging to the genus Leishmania and affects millions worldwide. This disease is mainly prevalent in tropical and subtropical regions and is associated with a high risk of public morbidity and mortality if left untreated. Transmission of this deadly disease is aggravated by the bite of female sand-fly vectors (Phlebotomus and Lutzomyia). With time, significant advancement in leishmaniasis-related research has been carried out to cope with the disease burden. Still, the Leishmania parasite has also co-evolved with its host and adapted successfully within the host's lethal milieu/environment. Thus, understanding and knowledge of various leishmanial virulence factors responsible for the parasitic infection are essential for exploring drug targets and vaccine candidates. The present review elucidates the importance of virulence factors in pathogenesis and summarizes the major leishmanial virulence molecules contributing to the parasitic infection during host-pathogen interaction. Furthermore, we have also elaborated on the potential contribution of leishmanial virulence proteins in developing vaccine candidates and exploring novel therapeutics against this parasitic disease. We aim to represent a clearer picture of parasite pathogenesis within the human host that can further aid in unraveling new strategies to fight against the deadly infection of leishmaniasis.

Elevated baseline expression of seven virulence factor RNA transcripts in visceralizing species of Leishmania: a preliminary quantitative PCR study

Introduction:

Leishmaniasis is a neglected tropical disease that manifests as three major disease phenotypes: cutaneous, mucocutaneous, and visceral. In this preliminary study, we quantified virulence factor (VF) RNA transcript expression in Leishmania species, stratified by geographic origin and propensity for specific disease phenotypes.

Methods:

Cultured promastigotes of 19 Leishmania clinical and ATCC isolates were extracted for total cellular RNA, cDNA was reverse transcribed, and qPCR assays were performed to quantify VF RNA transcript expression for hsp23, hsp70, hsp83, hsp100, mpi, cpb, and gp63.

Results:

Comparison of visceralizing species (Leishmania donovani, Leishmania chagasi, and Leishmania infantum) versus non-visceralizing species [Leishmania (Viannia) spp., Leishmania tropica, Leishmania major, Leishmania mexicana, and Leishmania amazonensis] revealed a significantly greater pooled transcript expression for visceralizing species (p = 0.0032). Similarly, Old World species demonstrated significantly higher VF RNA transcript expression than New World species (p = 0.0015). On a per-gene basis, species with a propensity to visceralize ubiquitously expressed higher levels of gp63 (p = 0.005), cpb (p = 0.0032), mpi (p = 0.0032), hsp23 (p = 0.0039), hsp70 (p = 0.0032), hsp83 (p = 0.0032), and hsp100 (p = 0.0032).

Conclusion:

Here, we provide quantitative, preliminary evidence of elevated VF RNA transcript expression driven largely by the visceralizing causative species of Leishmania. This work highlights the extensive heterogeneity in pathogenicity mechanisms between Leishmania species, which may partly underpin the fatal progression of visceral leishmaniasis.

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.

The Astonishing Large Family of HSP40/DnaJ Proteins Existing in Leishmania

Abrupt environmental changes are faced by Leishmania parasites during transmission from a poikilothermic insect vector to a warm-blooded host. Adaptation to harsh environmental conditions, such as nutrient deprivation, hypoxia, oxidative stress and heat shock needs to be accomplished by rapid reconfiguration of gene expression and remodeling of protein interaction networks. Chaperones play a central role in the maintenance of cellular homeostasis, and they are responsible for crucial tasks such as correct folding of nascent proteins, protein translocation across different subcellular compartments, avoiding protein aggregates and elimination of damaged proteins. Nearly one percent of the gene content in the Leishmania genome corresponds to members of the HSP40 family, a group of proteins that assist HSP70s in a variety of cellular functions. Despite their expected relevance in the parasite biology and infectivity, little is known about their functions or partnership with the different Leishmania HSP70s. Here, we summarize the structural features of the 72 HSP40 proteins encoded in the Leishmania infantum genome and their classification into four categories. A review of proteomic data, together with orthology analyses, allow us to postulate cellular locations and possible functional roles for some of them. A detailed study of the members of this family would provide valuable information and opportunities for drug discovery and improvement of current treatments against leishmaniasis.

Effect of the endoplasmic reticulum stressor tunicamycin in Angomonas deanei heat-shock protein expression and on the association with the endosymbiotic bacterium

The endoplasmic reticulum (ER) presents unique properties to establishing bacterium symbiosis in eukaryotic cells since it synthesizes and glycosylates essential molecules like proteins and lipids. Tunicamycin (TM) is an antibiotic that inhibits the first step in the N-linked glycosylation in eukaryotes and has been used as an ER stress inducer to activate the Unfolded Protein Response (UPR). Mutualistic symbiosis in trypanosomatids is characterized by structural adaptations and intense metabolic exchanges, thus we investigated the effects of TM in the association between Angomonas deanei and its symbiotic bacterium, through ultrastructural and proteomic approaches. Cells treated with the inhibitor showed a decrease in proliferation, enlargement of the ER and Golgi cisternae and an increased distance between the symbiont and the ER. TM proved to be an important tool to better understand ER stress in trypanosomatids, since changes in protein composition were observed in the host protozoan, especially the expression of the Hsp90 chaperone. Furthermore, data obtained indicates the importance of the ER for the adaptation and maintenance of symbiotic associations between prokaryotes and eukaryotes, considering that this organelle has recognized importance in the biogenesis and division of cell structures.

Profilin is involved in G1 to S phase progression and mitotic spindle orientation during Leishmania donovani cell division cycle

Profilin is a multi-ligand binding protein, which is a key regulator of actin dynamics and involved in regulating several cellular functions. It is present in all eukaryotes, including trypanosomatids such as Leishmania. However, not much is known about its functions in these organisms. Our earlier studies have shown that Leishmania parasites express a single homologue of profilin (LdPfn) that binds actin, phosphoinositides and poly- L- proline motives, and depletion of its intracellular pool to 50%of normal levels affects the cell growth and intracellular trafficking. Here, we show, employing affinity pull-down and mass spectroscopy, that LdPfn interacted with a large number of proteins, including those involved in mRNA processing and protein translation initiation, such as eIF4A1. Further, we reveal, using mRNA Seq analysis, that depletion of LdPfn in Leishmania cells (LdPfn^+/-) resulted in significantly reduced expression of genes which encode proteins involved in cell cycle regulation, mRNA translation initiation, nucleosides and amino acids transport. In addition, we show that in LdPfn^+/- cells, cellular levels of eIF4A1 protein were significantly decreased, and during their cell division cycle, G1-to-S phase progression was delayed and orientation of mitotic spindle altered. These changes were, however, reversed to normal by episomal expression of GFP-LdPfn in LdPfn^+/- cells. Taken together, our results indicate that profilin is involved in regulation of G1-to-S phase progression and mitotic spindle orientation in Leishmania cell cycle, perhaps through its interaction with elF4A1 protein.

Transcriptomic Profile of Canine DH82 Macrophages Infected by Leishmania infantum Promastigotes with Different Virulence Behavior

Zoonotic visceral leishmaniosis caused by Leishmania infantum is an endemic disease in the Mediterranean Basin affecting mainly humans and dogs, the main reservoir. The leishmaniosis outbreak declared in the Community of Madrid (Spain) led to a significant increase in human disease incidence without enhancing canine leishmaniosis prevalence, suggesting a better adaptation of the outbreak's isolates by other host species. One of the isolates obtained in the focus, IPER/ES/2012/BOS1FL1 (BOS1FL1), has previously demonstrated a different phenotype than the reference strain MCAN/ES/1996/BCN150 (BCN150), characterized by a lower infectivity when interacting with canine macrophages. Nevertheless, not enough changes in the cell defensive response were found to support their different behavior. Thus, we decided to investigate the molecular mechanisms involved in the interaction of both parasites with DH82 canine macrophages by studying their transcriptomic profiles developed after infection using RNA sequencing. The results showed a common regulation induced by both parasites in the phosphoinositide-3-kinase-protein kinase B/Akt and NOD-like receptor signaling pathways. However, other pathways, such as phagocytosis and signal transduction, including tumor necrosis factor, mitogen-activated kinases and nuclear factor-κB, were only regulated after infection with BOS1FL1. These differences could contribute to the reduced infection ability of the outbreak isolates in canine cells. Our results open a new avenue to investigate the true role of adaptation of L. infantum isolates in their interaction with their different hosts.

Immunological characterization of rLdTCP1γ for its prophylactic potential against visceral leishmaniasis in hamster model

Visceral leishmaniasis (VL) is a chronic tropical disease responsible for devastating epidemics worldwide. Though current treatment relies on drugs, the emergence of resistance, toxic side-effects, and strenuous administration has led to an ineffective remedy. Hence, vaccination remains an alternative and desirable approach for VL control. Though extensive research on anti-leishmanial vaccine candidates has been carried out in past decades, presence of an effective molecule is still missing. In the present study, we have evaluated the immunogenicity and prophylactic potential of a recombinant T-complex protein-1 gamma subunit of L. donovani (rLdTCP1γ), against VL in hamster model. The antigen exhibited in vitro stimulation of lymphoproliferative and NO response in miltefosine and amphotericin B treated hamsters depicting its immunotherapeutic/immunogenic nature. Immunization with rLdTCP1γ revealed a strong protective response against experimental VL as indicated by reduced parasite load in the spleen of immunized group compared to infected control. The immunized animals gained body weight and exhibited significant reduction in the spleen and liver weight as compared to infected controls on days 60, 90, 120 post-challenge. A substantial augmentation of cell-mediated immune response as depicted by an increased lymphocyte proliferation, nitric oxide production, DTH responses and increased levels of IgG2 was observed in rLdTCP1γ immunized hamsters. The Th1 stimulatory potential, imparted by the antigen, was found to be intensified in the presence of adjuvant Bacillus Calmette-Guérin (BCG). The efficacy was further assisted by an upregulated mRNA transcript of Th1 induced cytokines (IL-12, IFN-γ and TNFα) and downregulation of IL-4 and IL-10. The results are thus suggestive of rLdTCP1γ having the potential of a strong vaccine candidate against VL.

Comparative phosphoproteomic analysis unravels MAPK1 regulated phosphoproteins in Leishmania donovani

Mitogen Activated Protein Kinase1 (MAPK1) of Leishmania donovani functions as key regulators of various cellular activities, which seem to be imperative for parasite survival, infectivity, drug resistance and post-translational modification of chaperones/co-chaperones. However, very less is known about LdMAPK1 target proteins. With recent advancements in proteomics, we aimed to identify phosphoproteins which were differentially expressed in LdMAPK1 overexpressing (Dd8++/++) and single replacement mutants (Dd8+/) as compared to wild type (Dd8+/+) parasites, utilizing LC-MS/MS approach. An in-depth label-free phospoproteomic analysis revealed that modulation of LdMAPK1 expression significantly modulates expression levels of miscellaneous phosphoproteins which may act as its targets/substrates. Out of 1974 quantified phosphoproteins in parasite, 140 were significantly differentially expressed in MAPK1 overexpressing and single replacement mutants. These differentially expressed phosphoproteins are majorly associated with metabolism, signal transduction, replication, transcription, translation, transporters and cytoskeleton/motor proteins, hence suggested that MAPK1 may act in concert to modulate global biological processes. The study further implicated possible role of LdMAPK1 in regulation and management of stress machinery in parasite through post translational modifications. Precisely, comparative phosphoproteomics study has elucidated significant role of LdMAPK1 in regulating various pathways contributing in parasite biology with relevance to future drug development. SIGNIFICANCE: MAPKinase1, the downstream kinase of MAPK signal transduction pathway, has drawn much attention as potential therapeutic drug target due to their indispensable role in survival and infectivity of Leishmania donovani. However, limited information is available about its downstream effector proteins/signaling networks. Utilizing label free LC-MS/MS analysis, phosphoproteome of LdMAPK1 over-expressing (Dd8++/++) and LdMAPK1 single replacement mutants (Dd8+/-) with wild type (Dd8+/+) parasites was compared and identified 140 LdMAPK1 modulated phosphoproteins, mainly involved in pathways like signal transduction, metabolism, transcriptional, translational, post-translational modification and regulation of heat shock proteins. Interestingly, LdMAPK1 interacts directly with only six phosphoproteins i.e. casein kinase, casein kinase II, HSP83/HSP90, LACK, protein kinase and serine/threonine protein kinase. Thus, the study elucidates significant role of LdMAPK1 in Leishmania biology which may drive drug-discovery efforts against visceral leishmaniasis.

Potential therapeutic targets shared between leishmaniasis and cancer

The association of leishmaniasis and malignancies in human and animal models has been highlighted in recent years. The misdiagnosis of coexistence of leishmaniasis and cancer and the use of common drugs in the treatment of such diseases prompt us to further survey the molecular biology of Leishmania parasites and cancer cells. The information regarding common expressed proteins, as possible therapeutic targets, in Leishmania parasites and cancer cells is scarce. Therefore, the current study reviews proteins, and investigates the regulation and functions of several key proteins in Leishmania parasites and cancer cells. The up- and down-regulations of such proteins were mostly related to survival, development, pathogenicity, metabolic pathways and vital signalling in Leishmania parasites and cancer cells. The presence of common expressed proteins in Leishmania parasites and cancer cells reveals valuable information regarding the possible shared mechanisms of pathogenicity and opportunities for therapeutic targeting in leishmaniasis and cancers in the future.

Heat Shock Proteins as the Druggable Targets in Leishmaniasis: Promises and Perils

Leishmania, the causative agent of leishmaniasis, is an intracellular pathogen that thrives in the insect gut and mammalian macrophages to complete its life cycle. Apart from temperature difference (26 to 37°C), it encounters several harsh conditions, including oxidative stress, inflammatory reactions, and low pH. Heat shock proteins (HSPs) play essential roles in cell survival by strategically reprogramming cellular processes and signaling pathways. HSPs assist cells in multiple functions, including differentiation, adaptation, virulence, and persistence in the host cell. Due to cyclical epidemiological patterns, limited chemotherapeutic options, drug resistance, and the absence of a vaccine, control of leishmaniasis remains a far-fetched dream. The essential roles of HSPs in parasitic differentiation and virulence and increased expression in drug-resistant strains highlight their importance in combating the disease. In this review, we highlighted the diverse physiological importance of HSPs present in Leishmania, emphasizing their significance in disease pathogenesis. Subsequently, we assessed the potential of HSPs as a chemotherapeutic target and underlined the challenges associated with it. Furthermore, we have summarized a few ongoing drug discovery initiatives that need to be explored further to develop clinically successful chemotherapeutic agents in the future.

General Structural and Functional Features of Molecular Chaperones

Molecular chaperones are a group of structurally diverse and highly conserved ubiquitous proteins. They play crucial roles in facilitating the correct folding of proteins in vivo by preventing protein aggregation or facilitating the appropriate folding and assembly of proteins. Heat shock proteins form the major class of molecular chaperones that are responsible for protein folding events in the cell. This is achieved by ATP-dependent (folding machines) or ATP-independent mechanisms (holders). Heat shock proteins are induced by a variety of stresses, besides heat shock. The large and varied heat shock protein class is categorised into several subfamilies based on their sizes in kDa namely, small Hsps (HSPB), J domain proteins (Hsp40/DNAJ), Hsp60 (HSPD/E; Chaperonins), Hsp70 (HSPA), Hsp90 (HSPC), and Hsp100. Heat shock proteins are localised to different compartments in the cell to carry out tasks specific to their environment. Most heat shock proteins form large oligomeric structures, and their functions are usually regulated by a variety of cochaperones and cofactors. Heat shock proteins do not function in isolation but are rather part of the chaperone network in the cell. The general structural and functional features of the major heat shock protein families are discussed, including their roles in human disease. Their function is particularly important in disease due to increased stress in the cell. Vector-borne parasites affecting human health encounter stress during transmission between invertebrate vectors and mammalian hosts. Members of the main classes of heat shock proteins are all represented in Plasmodium falciparum, the causative agent of cerebral malaria, and they play specific functions in differentiation, cytoprotection, signal transduction, and virulence.

Comparative transcriptomic analysis of antimony resistant and susceptible Leishmania infantum lines

Background

One of the major challenges to leishmaniasis treatment is the emergence of parasites resistant to antimony. To study differentially expressed genes associated with drug resistance, we performed a comparative transcriptomic analysis between wild-type and potassium antimonyl tartrate (Sb^III)-resistant Leishmania infantum lines using high-throughput RNA sequencing.

Methods

All the cDNA libraries were constructed from promastigote forms of each line, sequenced and analyzed using STAR for mapping the reads against the reference genome (L. infantum JPCM5) and DESeq2 for differential expression statistical analyses. All the genes were functionally annotated using sequence similarity search.

Results

The analytical pipeline considering an adjusted p-value < 0.05 and fold change > 2.0 identified 933 transcripts differentially expressed (DE) between wild-type and Sb^III-resistant L. infantum lines. Out of 933 DE transcripts, 504 presented functional annotation and 429 were assigned as hypothetical proteins. A total of 837 transcripts were upregulated and 96 were downregulated in the Sb^III-resistant L. infantum line. Using this DE dataset, the proteins were further grouped in functional classes according to the gene ontology database. The functional enrichment analysis for biological processes showed that the upregulated transcripts in the Sb^III-resistant line are associated with protein phosphorylation, microtubule-based movement, ubiquitination, host–parasite interaction, cellular process and other categories. The downregulated transcripts in the Sb^III-resistant line are assigned in the GO categories: ribonucleoprotein complex, ribosome biogenesis, rRNA processing, nucleosome assembly and translation.

Conclusions

The transcriptomic profile of L. infantum showed a robust set of genes from different metabolic pathways associated with the antimony resistance phenotype in this parasite. Our results address the complex and multifactorial antimony resistance mechanisms in Leishmania, identifying several candidate genes that may be further evaluated as molecular targets for chemotherapy of leishmaniasis.

The Experimental Proteome of Leishmania infantum Promastigote and Its Usefulness for Improving Gene Annotations

Leishmania infantum causes visceral leishmaniasis (kala-azar), the most severe form of leishmaniasis, which is lethal if untreated. A few years ago, the re-sequencing and de novo assembling of the L. infantum (JPCM5 strain) genome was accomplished, and now we aimed to describe and characterize the experimental proteome of this species. In this work, we performed a proteomic analysis from axenic cultured promastigotes and carried out a detailed comparison with other Leishmania experimental proteomes published to date. We identified 2352 proteins based on a search of mass spectrometry data against a database built from the six-frame translated genome sequence of L. infantum. We detected many proteins belonging to organelles such as glycosomes, mitochondria, or flagellum, as well as many metabolic enzymes and many putative RNA binding proteins and molecular chaperones. Moreover, we listed some proteins presenting post-translational modifications, such as phosphorylations, acetylations, and methylations. On the other hand, the identification of peptides mapping to genomic regions previously annotated as non-coding allowed for the correction of annotations, leading to the N-terminal extension of protein sequences and the uncovering of eight novel protein-coding genes. The alliance of proteomics, genomics, and transcriptomics has resulted in a powerful combination for improving the annotation of the L. infantum reference genome.

Screening for Small Molecule Modulators of Trypanosoma brucei Hsp70 Chaperone Activity Based upon Alcyonarian Coral-Derived Natural Products

The Trypanosoma brucei Hsp70/J-protein machinery plays an essential role in survival, differentiation, and pathogenesis of the protozoan parasite, and is an emerging target against African Trypanosomiasis. This study evaluated a set of small molecules, inspired by the malonganenones and nuttingins, as modulators of the chaperone activity of the cytosolic heat inducible T. brucei Hsp70 and constitutive TbHsp70.4 proteins. The compounds were assessed for cytotoxicity on both the bloodstream form of T. b. brucei parasites and a mammalian cell line. The compounds were then investigated for their modulatory effect on the aggregation suppression and ATPase activities of the TbHsp70 proteins. A structure-activity relationship for the malonganenone-class of alkaloids is proposed based upon these results.

Early antibody response and clinical outcome in experimental canine leishmaniasis

Infected dogs are the main reservoir of zoonotic visceral leishmaniasis, a widespread parasitic disease caused by Leishmania infantum. Therefore, the control of canine infections is required to reduce the incidence of human cases. Disease outcome in dogs depends on the fine balance between parasite virulence and efficacy of the immune system. Thus, knowledge of early response could yield relevant information for diagnosis and follow-up. In our study, 20 Beagle dogs were intravenously infected with 10⁸ amastigotes of a fresh isolate of L. infantum and monitored along 16 weeks post inoculation. Specific antibody response and clinical evolution of infected animals were highly variable. Immunofluorescence antibody test (IFAT) and enzyme linked immunosorbent assay (ELISA) were useful to assess infection status, although only ELISA with promastigote-coated plates and, particularly, western blotting (WB) allowed an early diagnosis. Prominent antigens were identified by mass peptide fingerprinting. Chaperonin HSP60, 32 and 30 KDa antigens were recognized by all dogs on week 10 post infection. This suggests that these antigens may be valuable for early diagnosis. Advanced infection showed, in addition, reactivity to HSP83 and HSP70. Disease outcome did not show a clear relationship with ELISA or IFAT titers. Correlation between the clinical status and the combined reactivity to some antigens sustains their use for diagnosis and follow-up.

Trypanosoma brucei J-Protein 2 Functionally Co-Operates with the Cytosolic Hsp70 and Hsp70.4 Proteins

The etiological agent of African trypanosomiasis, Trypanosoma brucei (Tb), has been identified to possess an expanded and diverse group of heat shock proteins, which have been implicated in cytoprotection, differentiation, and subsequently progression and transmission of the disease. Heat shock protein 70 (Hsp70) is a highly conserved and ubiquitous molecular chaperone that is important in maintaining protein homeostasis in the cell. Its function is regulated by a wide range of co-chaperones, and inhibition of these functions and interactions with co-chaperones are emerging as potential therapeutic targets for numerous diseases. This study sought to biochemically characterize the cytosolic TbHsp70 and TbHsp70.4 proteins and to investigate if they functionally co-operate with the Type I J-protein, Tbj2. Expression of TbHsp70 was shown to be heat inducible, while TbHsp70.4 was constitutively expressed. The basal ATPase activities of TbHsp70.4 and TbHsp70 were stimulated by Tbj2. It was further determined that Tbj2 functionally co-operated with TbHsp70 and TbHsp70.4 as the J-protein was shown to stimulate the ability of both proteins to mediate the refolding of chemically denatured β-galactosidase. This study provides further insight into this important class of proteins, which may contribute to the development of new therapeutic strategies to combat African Trypanosomiasis.

Protein quality control machinery in intracellular protozoan parasites: hopes and challenges for therapeutic targeting

Intracellular protozoan parasites have evolved an efficient protein quality control (PQC) network comprising protein folding and degradation machineries that protect the parasite's proteome from environmental perturbations and threats posed by host immune surveillance. Interestingly, the components of PQC machinery in parasites have acquired sequence insertions which may provide additional interaction interfaces and diversify the repertoire of their biological roles. However, the auxiliary functions of PQC machinery remain poorly explored in parasite. A comprehensive understanding of this critical machinery may help to identify robust biological targets for new drugs against acute or latent and drug-resistant infections. Here, we review the dynamic roles of PQC machinery in creating a safe haven for parasite survival in hostile environments, serving as a metabolic sensor to trigger transformation into phenotypically distinct stages, acting as a lynchpin for trafficking of parasite cargo across host membrane for immune evasion and serving as an evolutionary capacitor to buffer mutations and drug-induced proteotoxicity. Versatile roles of PQC machinery open avenues for exploration of new drug targets for anti-parasitic intervention and design of strategies for identification of potential biomarkers for point-of-care diagnosis.

Artemisinin-resistant Leishmania parasite modulates host cell defense mechanism and exhibits altered expression of unfolded protein response genes

Artemisinin, extracted from a medicinal herb Artemisia annua, is widely used to treat malaria and has shown potent anticancer activity. Artemisinin has been found to be effective against experimental visceral and cutaneous leishmaniasis. Despite extensive research to understand the complex mechanism of resistance to artemisinin, several questions remain unanswered. The artesunate (ART)-resistant line of Leishmania donovani was selected and cellular mechanisms associated with resistance to artemisinin were investigated. ART-resistant (AS-R) parasites showed reduced susceptibility towards ART both at promastigote and amastigote stage compared with ART sensitive (WT) parasites. WT and AS-R parasites were both more susceptible to ART at the early log phase of growth compared with late log phase. AS-R parasites were more infective to the host macrophages (p < 0.05). Evaluation of parasites' tolerance towards host microbicidal mechanisms revealed that AS-R parasites were more tolerant to complement-mediated lysis and nitrosative stress. ROS levels were modulated in presence of ART in AS-R parasites infected macrophages. Interestingly, infection of macrophages by AS-R parasites led to modulated levels of host interleukins, IL-2 and IL-10, in addition to nitric oxide. Additionally, AS-R parasites showed upregulated expression of genes of unfolded protein response pathway including methyltransferase domain-containing protein (HSP40) and flagellar attachment zone protein (prefoldin), that are reported to be associated with ART resistance in Plasmodium falciparum malaria. This study presents in vitro model of artemisinin-resistant Leishmania parasite and cellular mechanisms associated with ART resistance in Leishmania.

An immunoproteomic approach to identifying immunoreactive proteins in Leishmania infantum amastigotes using sera of dogs infected with canine visceral leishmaniasis

Visceral leishmaniasis (VL), the most severe form of leishmaniasis, is caused by Leishmania donovani and Leishmania infantum. The infected dogs with canine visceral leishmaniasis (CVL) are important reservoirs for VL in humans, so the diagnosis, treatment and vaccination of the infected dogs will ultimately decrease the rate of human VL. Proteomics and immunoproteomics techniques have facilitated the introduction of novel drug, vaccine and diagnostic targets. Our immunoproteomic study was conducted to identify new immunoreactive proteins in amastigote form of L. infantum. The strain of L. infantum (MCAN/IR/07/Moheb-gh) was obtained from CVL-infected dogs. J774 macrophage cells were infected with the L. infantum promastigotes. The infected macrophages were ruptured, and pure amastigotes were extracted from the macrophages. After protein extraction, two-dimensional gel electrophoresis was employed for protein separation followed by Western blotting. Western blotting was performed, using symptomatic and asymptomatic sera of the infected dogs with CVL. Thirteen repeatable immunoreactive spots were identified by Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Some, including prohibitin, ornithine aminotransferase, annexin A4, and apolipoprotein A-I, have been critically involved in metabolic pathways, survival, and pathogenicity of Leishmania parasites. Further investigations are required to confirm our identified immunoreactive proteins as a biomarker for CVL.

Analysis by RNA-seq of transcriptomic changes elicited by heat shock in Leishmania major

Besides their medical relevance, Leishmania is an adequate model for studying post-transcriptional mechanisms of gene expression. In this microorganism, mRNA degradation/stabilization mechanisms together with translational control and post-translational modifications of proteins are the major drivers of gene expression. Leishmania parasites develop as promastigotes in sandflies and as amastigotes in mammalians, and during host transmission, the parasite experiences a sudden temperature increase. Here, changes in the transcriptome of Leishmania major promastigotes after a moderate heat shock were analysed by RNA-seq. Several of the up-regulated transcripts code for heat shock proteins, other for proteins previously reported to be amastigote-specific and many for hypothetical proteins. Many of the transcripts experiencing a decrease in their steady-state levels code for transporters, proteins involved in RNA metabolism or translational factors. In addition, putative long noncoding RNAs were identified among the differentially expressed transcripts. Finally, temperature-dependent changes in the selection of the spliced leader addition sites were inferred from the RNA-seq data, and particular cases were further validated by RT-PCR and Northern blotting. This study provides new insights into the post-transcriptional mechanisms by which Leishmania modulate gene expression.

Virulence factor RNA transcript expression in the Leishmania Viannia subgenus: influence of species, isolate source, and Leishmania RNA virus-1

BACKGROUND

Leishmania RNA virus-1 (LRV1) is a double-stranded RNA virus identified in 20-25% of Viannia-species endemic to Latin America, and is believed to accelerate cutaneous to mucosal leishmaniasis over time. Our objective was to quantify known virulence factor (VF) RNA transcript expression according to LRV1 status, causative species, and isolate source.

METHODS

Eight cultured isolates of Leishmania were used, four of which were LRV1-positive (Leishmania Viannia braziliensis [n = 1], L. (V.) guyanensis [n = 1], L. (V.) panamensis [n = 2]), and four were LRV1-negative (L. (V.) panamensis [n = 3], L. (V.) braziliensis [n = 1]). Promastigotes were inoculated into macrophage cultures, and harvested at 24 and 48 h. RNA transcript expression of hsp23, hsp70, hsp90, hsp100, mpi, cpb, and gp63 were quantified by qPCR.

RESULTS

RNA transcript expression of hsp100 (p = 0.012), cpb (p = 0.016), and mpi (p = 0.022) showed significant increases from baseline pure culture expression to 24- and 48-h post-macrophage infection, whereas hsp70 (p = 0.004) was significantly decreased. A trend toward increased transcript expression of hsp100 at baseline in isolates of L. (V.) panamensis was noted. Pooled VF RNA transcript expression by L. (V.) panamensis isolates was lower than that of L. (V.) braziliensis and L. (V.) guyananesis at 24 h (p = 0.03). VF RNA transcript expression did not differ by LRV1 status, or source of cultured isolate at baseline, 24, or 48 h; however, a trend toward increased VF RNA transcript expression of 2.71- and 1.93-fold change of mpi (p = 0.11) and hsp90 (p = 0.11), respectively, in LRV1 negative isolates was noted. Similarly, a trend toward lower levels of overall VF RNA transcript expression in clinical isolates (1.15-fold change) compared to ATCC® strains at 24 h was noted (p = 0.07).

CONCLUSIONS

Our findings suggest that known VF RNA transcript expression may be affected by the process of macrophage infection. We were unable to demonstrate definitively that LRV-1 presence affected VF RNA transcript expression in the species and isolates studied. L. (V.) guyanensis and L. (V.) braziliensis demonstrated higher pooled VF RNA transcript expression than L. (V.) panamensis; however, further analyses of protein expression to corroborate this finding are warranted.

Comparative transcriptomics in Leishmania braziliensis: disclosing differential gene expression of coding and putative noncoding RNAs across developmental stages

Leishmaniasis is a worldwide public health problem caused by protozoan parasites of the genus Leishmania. Leishmania braziliensis is the most important species responsible for tegumentary leishmaniases in Brazil. An understanding of the molecular mechanisms underlying the success of this parasite is urgently needed. An in-depth study on the modulation of gene expression across the life cycle stages of L. braziliensis covering coding and noncoding RNAs (ncRNAs) was missing and is presented herein. Analyses of differentially expressed (DE) genes revealed that most prominent differences were observed between the transcriptomes of insect and mammalian proliferative forms (6,576 genes). Gene ontology (GO) analysis indicated stage-specific enriched biological processes. A computational pipeline and 5 ncRNA predictors allowed the identification of 11,372 putative ncRNAs. Most of the DE ncRNAs were found between the transcriptomes of insect and mammalian proliferative stages (38%). Of the DE ncRNAs, 295 were DE in all three stages and displayed a wide range of lengths, chromosomal distributions and locations; many of them had a distinct expression profile compared to that of their protein-coding neighbors. Thirty-five putative ncRNAs were submitted to northern blotting analysis, and one or more hybridization-positive signals were observed in 22 of these ncRNAs. This work presents an overview of the L. braziliensis transcriptome and its adjustments throughout development. In addition to determining the general features of the transcriptome at each life stage and the profile of protein-coding transcripts, we identified and characterized a variety of noncoding transcripts. The novel putative ncRNAs uncovered in L. braziliensis might be regulatory elements to be further investigated.

The Hsp70/J-protein machinery of the African trypanosome, Trypanosoma brucei

The etiological agent of the neglected tropical disease African trypanosomiasis, Trypanosoma brucei, possesses an expanded and diverse repertoire of heat shock proteins, which have been implicated in cytoprotection, differentiation, as well as progression and transmission of the disease. Hsp70 plays a crucial role in proteostasis, and inhibition of its interactions with co-chaperones is emerging as a potential therapeutic target for numerous diseases. In light of genome annotations and the release of the genome sequence of the human infective subspecies, an updated and current in silico overview of the Hsp70/J-protein machinery in both T. brucei brucei and T. brucei gambiense was conducted. Functional, structural, and evolutionary analyses of the T. brucei Hsp70 and J-protein families were performed. The Hsp70 and J-proteins from humans and selected kinetoplastid parasites were used to assist in identifying proteins from T. brucei, as well as the prediction of potential Hsp70-J-protein partnerships. The Hsp70 and J-proteins were mined from numerous genome-wide proteomics studies, which included different lifecycle stages and subcellular localisations. In this study, 12 putative Hsp70 proteins and 67 putative J-proteins were identified to be encoded on the genomes of both T. brucei subspecies. Interestingly there are 6 type III J-proteins that possess tetratricopeptide repeat-containing (TPR) motifs. Overall, it is envisioned that the results of this study will provide a future context for studying the biology of the African trypanosome and evaluating Hsp70 and J-protein interactions as potential drug targets.

Western Blot Analysis of Leishmania infantum Antigens in Sera of Patients with Visceral Leishmaniasis

BACKGROUND

Visceral leishmaniasis (VL) is endemic in the northwest and south of Iran. Untreated cases of VL could cause death. The aim of the present study was to evaluate the diagnostic performance of western blotting to detect a specific immunodominant proteins pattern for Leishmania infantum infection using human sera infected with VL.

METHODS

We studied a panel of 122 cryopreserved human serum samples from the leishmaniasis Research Laboratory, Tehran University of Medical Sciences, Tehran, Iran from 2010 to 2017.Serum samples were collected from visceral (Group I, n: 43) and cutaneous leishmaniasis (CL) (Group II, n: 8) patients, healthy individuals from endemic (Group III, n: 13) and non-endemic (Group IV, n: 16) areas for VL, and patients with other infectious diseases (Group V, n: 42). Total antigens were prepared from the Iranian strain of L. infantum promastigote form.

RESULTS

In western blotting method, 34 protein bands of 14 to 163 kDa were recognized using the sera of VL patients. The polypeptide fractions with the highest frequency including 29, 51, and 62 kDa fractions were detected using 81.4%, 79%, and 81.4% of the sera, respectively. These bands were not detected using the sera of the negative control. Moreover, 19-23, 27, 31-35, 143-163, and 109 kDa fractions were detected specifically using the sera of the patients with VL.

CONCLUSION

This technique could be a primary step for further exploration of VL immunodominant antigens for cloning (or any technique) further investigations for future planning.

The Autophagy-Lysosomal Pathways and Their Emerging Roles in Modulating Proteostasis in Tumors

In normal physiological condition, the maintenance of cellular proteostasis is a prerequisite for cell growth, functioning, adapting to changing micro-environments, and responding to extracellular stress. Cellular proteostasis is maintained by specific proteostasis networks (PNs) to prevent protein misfolding, aggregating, and accumulating in subcellular compartments. Commonly, the PNs are composed of protein synthesis, molecular chaperones, endoplasmic reticulum (ER), unfolded protein response (UPR), stress response pathways (SRPs), secretions, ubiquitin proteasome system (UPS), and autophagy-lysosomal pathways (ALPs). Although great efforts have been made to explore the underlying detailed mechanisms of proteostasis, there are many questions remain to explore, especially in proteostasis regulated by the ALPs. Proteostasis out-off-balance is correlated with various human diseases such as diabetes, stroke, inflammation, hypertension, pulmonary fibrosis, and Alzheimer’s disease. Enhanced regulation of PNs is observed in tumors, thereby indicating that proteostasis may play a pivotal role in tumorigenesis and cancer development. Recently, inhibitors targeting the UPS have shown to be failed in solid tumor treatment. However, there is growing evidence showing that the ALPs play important roles in regulation of proteostasis alone or with a crosstalk with other PNs in tumors. In this review, we provide insights into the proteostatic process and how it is regulated by the ALPs, such as macroautophagy, aggrephagy, chaperone-mediated autophagy, microautophagy, as well as mitophagy during tumor development.

Genome-wide identification of evolutionarily conserved Small Heat-Shock and eight other proteins bearing α-crystallin domain-like in kinetoplastid protists

Small Heat-Shock Proteins (sHSPs) and other proteins bearing alpha-crystallin domains (ACD) participate in defense against heat and oxidative stress and play important roles in cell cycle, cytoskeleton dynamics, and immunological and pathological mechanisms in eukaryotes. However, little is known about these proteins in early-diverging lineages of protists such as the kinetoplastids. Here, ACD-like proteins (ACDp) were investigated in genomes of 61 species of 12 kinetoplastid genera, including Trypanosoma spp. (23 species of mammals, reptiles and frogs), Leishmania spp. (mammals and lizards), trypanosomatids of insects, Phytomonas spp. of plants, and bodonids. Comparison of ACDps based on domain architecture, predicted tertiary structure, phylogeny and genome organization reveals a kinetoplastid evolutionarily conserved repertoire, which diversified prior to trypanosomatid adaptation to parasitic life. We identified 9 ACDp orthologs classified in 8 families of TryACD: four previously recognized (HSP20, Tryp23A, Tryp23B and ATOM69), and four characterized for the first time in kinetoplastids (TryACDP, TrySGT1, TryDYX1C1 and TryNudC). A single copy of each ortholog was identified in each genome alongside TryNudC1/TrypNudC2 homologs and, overall, ACDPs were under strong selection pressures at main phylogenetic lineages. Transcripts of all ACDPs were identified across the life stages of T. cruzi, T. brucei and Leishmania spp., but proteomic profiles suggested that most ACDPs may be species- and stage-regulated. Our findings establish the basis for functional studies, and provided evolutionary and structural support for an underestimated repertoire of ACDps in the kinetoplastids.

Environmental Stress Responses of DnaJA1, DnaJB12 and DnaJC8 in Apis cerana cerana

DnaJ, also known as Hsp40, plays important roles in maintaining the normal physiological state of an organism under stress conditions by mediating essential processes, such as protein synthesis, degradation, folding and metabolism. However, the exact functions of most DnaJ members are not fully understood in insects. Here, we identified three genes, AccDnaJA1, AccDnaJB12, and AccDnaJC8, in Apis cerana cerana and explored their connection with the environmental stress response. Quantitative real-time PCR results showed that the mRNA levels of AccDnaJA1, AccDnaJB12, and AccDnaJC8 were all induced under cold, UV, H2O2 and different pesticides treatment. The expression patterns of AccDnaJB12 and AccDnaJC8 were upregulated by CdCl2 and HgCl2 stress, while the transcriptional levels of AccDnaJA1 were downregulated by CdCl2 and HgCl2 stress. Western blot findings further indicated that AccDnaJB12 protein levels were increased by some stress conditions. Knockdown of each of these three genes downregulated the transcriptional patterns of several stress response-related genes at different levels. Functional analysis further demonstrated that the resistance of A. cerana cerana to lambda-cyhalothrin stress was reduced with knockdown of AccDnaJA1, AccDnaJB12, or AccDnaJC8, indicating that these three genes may be involved in the tolerance to this pesticide. Taken together, these findings indicate that AccDnaJA1, AccDnaJB12, and AccDnaJC8 may play pivotal roles in the stress response by facilitating honeybee survival under some adverse circumstances. To our knowledge, this is the first report that reveals the roles of DnaJ family proteins under different adverse circumstances in A. cerana cerana.

Leishmania phosphatase PP5 is a regulator of HSP83 phosphorylation and essential for parasite pathogenicity

Leishmania parasites are responsible for important neglected diseases in humans and animals, ranging from self-healing cutaneous lesions to fatal visceral manifestations. During the infectious cycle, Leishmania differentiates from the extracellular flagellated promastigote to the intracellular pathogenic amastigote. Parasite differentiation is triggered by changes in environmental cues, mainly pH and temperature. In general, extracellular signals are translated into stage-specific gene expression by a cascade of reversible protein phosphorylation regulated by protein kinases and phosphatases. Though protein kinases have been actively studied as potential anti-parasitic drug targets, our understanding of the biology of protein phosphatases in Leishmania is poor. We have previously reported the principal analysis of a novel protein phosphatase 5 (PP5) in Leishmania species. Here, we assessed the role of PP5 in parasite pathogenicity, where we uncovered, using transgenic PP5 over-expressing and PP5 null-mutant parasites, its importance in metacyclogeneisis, maintaining HSP83 phosphorylation homeostasis and virulence. All together, our results indicate the importance of PP5 in regulating parasite stress and adaptation during differentiation, making this protein an attractive potential target for therapeutic intervention.

Prediction of Leishmania major Key Proteins Via Topological Analysis of Protein-Protein Interaction Network

Background:

Although leishmaniasis is regarded as a public health problem, no effective vaccine or decisive treatment has been introduced for this disease. Therefore, representing novel therapeutic proteins is essential. Protein-protein Interaction network analysis is a suitable tool to discover novel drug targets for leishmania major. To this aim, gene and protein expression data is used for instructing protein network and the key proteins are highlighted.

Materials and Methods:

In this computational and bioinformatics study, the protein/gene expression data related to leishmania major were studied, and 252 candidate proteins were extracted. Then, the protein networks of these proteins were explored and visualized by using String database and Cytoscape software. Finally, clustering and gene ontology were performed by MCODE and PANTHER databases, respectively.

Results:

Based on gene ontology analysis, most of the leishmania major proteins were located in cell compartments and membrane. Catalytic activity and binding were regarded as the relevant molecular functions and metabolic and cellular processes were the significant biological process. In this network analysis, UB-EP52, EF-2, chaperonin, Hsp70.4, Hsp60, tubulin alpha and beta chain, and ENOL and LACK were introduced as hub-bottleneck proteins. Based on clustering analysis, Lmjf.32.3270, ENOL and Lmjf.13.0290 were determined as seed proteins in each cluster.

Conclusion:

The results indicated that hub proteins play a significant role in pathogenesis and life cycle of leishmania major. Further studies of hubs will provide a better understanding of leishmaniasis mechanisms. Finally, these key hub proteins could be a suitable and helpful potential for drug targets and treating leishmaniasis by considering their validation.

Vaccination with a Leishmania infantum HSP70-II null mutant confers long-term protective immunity against Leishmania major infection in two mice models

Background

The immunization with genetically attenuated Leishmania cell lines has been associated to the induction of memory and effector T cell responses against Leishmania able to control subsequent challenges. A Leishmania infantum null mutant for the HSP70-II genes has been described, possessing a non-virulent phenotype.

Methodology/Principal findings

The L. infantum attenuated parasites (LiΔHSP70-II) were inoculated in BALB/c (intravenously and subcutaneously) and C57BL/6 (subcutaneously) mice. An asymptomatic infection was generated and parasites diminished progressively to become undetectable in most of the analyzed organs. However, inoculation resulted in the long-term induction of parasite specific IFN-γ responses able to control the disease caused by a challenge of L. major infective promastigotes. BALB/c susceptible mice showed very low lesion development and a drastic decrease in parasite burdens in the lymph nodes draining the site of infection and internal organs. C57BL/6 mice did not show clinical manifestation of disease, correlated to the rapid migration of Leishmania specific IFN-γ producing T cells to the site of infection.

Conclusion/Significance

Inoculation of the LiΔHSP70-II attenuated line activates mammalian immune system for inducing moderate pro-inflammatory responses. These responses are able to confer long-term protection in mice against the infection of L. major virulent parasites.

Despite numerous efforts made, a vaccine against leishmaniasis for humans is not available. Attempts based on parasite fractions or selected antigens failed to confer long lasting protection. On the other side, leishmanization, which consists in the inoculation of live virulent parasites in hidden parts of the body, is effective against cutaneous leishmaniasis in humans but objectionable in terms of biosafety. Some efforts have been made to design live vaccines to make leishmanization safer. A promising strategy is the development of genetically attenuated parasites, able to confer immunity without undesirable side effects. Here, we have employed an attenuated L. infantum line (LiΔHSP70-II) as a vaccine against heterologous challenge with L. major in two experimental models. Infection with LiΔHSP70-II parasites does not cause pathology and induces long-term protection based on the induction of IFN-γ producing T cells that are recruited rapidly and specifically to the site of challenge with the virulent parasites. These results support the idea of using attenuated parasites for vaccination.

Leishmania donovani chaperonin 10 regulates parasite internalization and intracellular survival in human macrophages

Protozoa of the genus Leishmania infect macrophages in their mammalian hosts causing a spectrum of diseases known as the leishmaniases. The search for leishmania effectors that support macrophage infection is a focus of significant interest. One such candidate is leishmania chaperonin 10 (CPN10) which is secreted in exosomes and may have immunosuppressive properties. Here, we report for the first time that leishmania CPN10 localizes to the cytosol of infected macrophages. Next, we generated two genetically modified strains of Leishmania donovani (Ld): one strain overexpressing CPN10 (CPN10+++) and the second, a CPN10 single allele knockdown (CPN10+/-), as the null mutant was lethal. When compared with the wild-type (WT) parental strain, CPN10+/- Ld showed higher infection rates and parasite loads in human macrophages after 24 h of infection. Conversely, CPN10+++ Ld was associated with lower initial infection rates. This unexpected apparent gain-of-function for the knockdown could have been explained either by enhanced parasite internalization or by enhanced intracellular survival. Paradoxically, we found that CPN10+/- leishmania were more readily internalized than WT Ld, but also displayed significantly impaired intracellular survival. This suggests that leishmania CPN10 negatively regulates the rate of parasite uptake by macrophages while being required for intracellular survival. Finally, quantitative proteomics identified an array of leishmania proteins whose expression was positively regulated by CPN10. In contrast, many macrophage proteins involved in innate immunity were negatively regulated by CPN10. Taken together, these findings identify leishmania CPN10 as a novel effector with broad based effects on macrophage cell regulation and parasite survival.

Species- and Strain-Specific Adaptation of the HSP70 Super Family in Pathogenic Trypanosomatids

All eukaryotic genomes encode multiple members of the heat shock protein 70 (HSP70) family, which evolved distinctive structural and functional features in response to specific environmental constraints. Phylogenetic analysis of this protein family thus can inform on genetic and molecular mechanisms that drive species-specific environmental adaptation. Here we use the eukaryotic pathogen Leishmania spp. as a model system to investigate the evolution of the HSP70 protein family in an early-branching eukaryote that is prone to gene amplification and adapts to cytotoxic host environments by stress-induced and chaperone-dependent stage differentiation. Combining phylogenetic and comparative analyses of trypanosomatid genomes, draft genome of Paratrypanosoma and recently published genome sequences of 204 L. donovani field isolates, we gained unique insight into the evolutionary dynamics of the Leishmania HSP70 protein family. We provide evidence for (i) significant evolutionary expansion of this protein family in Leishmania through gene amplification and functional specialization of highly conserved canonical HSP70 members, (ii) evolution of trypanosomatid-specific, non-canonical family members that likely gained ATPase-independent functions, and (iii) loss of one atypical HSP70 member in the Trypanosoma genus. Finally, we reveal considerable copy number variation of canonical cytoplasmic HSP70 in highly related L. donovani field isolates, thus identifying this locus as a potential hot spot of environment–genotype interaction. Our data draw a complex picture of the genetic history of HSP70 in trypanosomatids that is driven by the remarkable plasticity of the Leishmania genome to undergo massive intra-chromosomal gene amplification to compensate for the absence of regulated transcriptional control in these parasites.

HSP70 of Leishmania amazonensis alters resistance to different stresses and mitochondrial bioenergetics

The 70 kDa heat shock protein (HSP70) is a molecular chaperone that assists the parasite Leishmania in returning to homeostasis after being subjected to different types of stress during its life cycle. In the present study, we evaluated the effects of HSP70 transfection of L. amazonensis promastigotes (pTEX-HSP70) in terms of morphology, resistance, infectivity and mitochondrial bioenergetics. The pTEX-HSP70 promastigotes showed no ultrastructural morphological changes compared to control parasites. Interestingly, the pTEX-HSP70 promastigotes are resistant to heat shock, H2O2-induced oxidative stress and hyperbaric environments. Regarding the bioenergetics parameters, the pTEX-HSP70 parasites had higher respiratory rates and released less H2O2 than the control parasites. Nevertheless, the infectivity capacity of the parasites did not change, as verified by the infection of murine peritoneal macrophages and human macrophages, as well as the infection of BALB/c mice. Together, these results indicate that the overexpression of HSP70 protects L. amazonensis from stress, but does not interfere with its infective capacity.

Glutaredoxin-deficiency confers bloodstream Trypanosoma brucei with improved thermotolerance

As constituents of their unusual trypanothione-based thiol metabolism, African trypanosomes express two dithiol glutaredoxins (Grxs), a cytosolic Grx1 and a mitochondrial Grx2, with so far unknown biological functions. As revealed by gel shift assays, in the mammalian bloodstream form of Trypanosoma brucei, Grx1 is in the fully reduced state. Upon diamide treatment of the cells, Grx1 forms an active site disulfide bridge that is rapidly re-reduced after stress removal; Cys76, a conserved non-active site Cys remains in the thiol state. Deletion of both grx1 alleles does not result in any proliferation defect of neither the procyclic insect form nor the bloodstream form, even not under various stress conditions. In addition, the Grx1-deficient parasites are fully infectious in the mouse model. A functional compensation by Grx2 is unlikely as identical levels of Grx2 were found in wildtype and Grx1-deficient cells. In the classical hydroxyethyl disulfide assay, Grx1-deficient bloodstream cells display 50-60% of the activity of wildtype cells indicating that the cytosolic oxidoreductase accounts for a major part of the total deglutathionylation capacity of the parasite. Intriguingly, at elevated temperature, proliferation of the Grx1-deficient bloodstream parasites is significantly less affected compared to wildtype cells. When cultured for three days at 39°C, only 51% of the cells in the wildtype population retained normal morphology with single mitochondrial and nuclear DNA (1K1N), whereas 27% of the cells displayed ≥2K2N. In comparison, 64% of the Grx1-deficient cells kept the 1K1N phenotype and only 18% had ≥2K2N. The data suggest that Grx1 plays a role in the regulation of the thermotolerance of the parasites by (in)directly interfering with the progression of the cell cycle, a process that may comprise protein (de)glutathionylation step(s).

Simultaneous transcriptional profiling of Leishmania major and its murine macrophage host cell reveals insights into host-pathogen interactions

BACKGROUND

Parasites of the genus Leishmania are the causative agents of leishmaniasis, a group of diseases that range in manifestations from skin lesions to fatal visceral disease. The life cycle of Leishmania parasites is split between its insect vector and its mammalian host, where it resides primarily inside of macrophages. Once intracellular, Leishmania parasites must evade or deactivate the host's innate and adaptive immune responses in order to survive and replicate.

RESULTS

We performed transcriptome profiling using RNA-seq to simultaneously identify global changes in murine macrophage and L. major gene expression as the parasite entered and persisted within murine macrophages during the first 72 h of an infection. Differential gene expression, pathway, and gene ontology analyses enabled us to identify modulations in host and parasite responses during an infection. The most substantial and dynamic gene expression responses by both macrophage and parasite were observed during early infection. Murine genes related to both pro- and anti-inflammatory immune responses and glycolysis were substantially upregulated and genes related to lipid metabolism, biogenesis, and Fc gamma receptor-mediated phagocytosis were downregulated. Upregulated parasite genes included those aimed at mitigating the effects of an oxidative response by the host immune system while downregulated genes were related to translation, cell signaling, fatty acid biosynthesis, and flagellum structure.

CONCLUSIONS

The gene expression patterns identified in this work yield signatures that characterize multiple developmental stages of L. major parasites and the coordinated response of Leishmania-infected macrophages in the real-time setting of a dual biological system. This comprehensive dataset offers a clearer and more sensitive picture of the interplay between host and parasite during intracellular infection, providing additional insights into how pathogens are able to evade host defenses and modulate the biological functions of the cell in order to survive in the mammalian environment.