Inhibition of HSP90 distinctively modulates the global phosphoproteome of Leishmania mexicana developmental stages.

IMPORTANCE: In the unicellular parasites Leishmania spp., the etiological agents of leishmaniasis, a complex infectious disease that affects 98 countries in 5 continents, chemical inhibition of HSP90 protein leads to differentiation from promastigote to amastigote stage. Recent studies indicate potential role for protein phosphorylation in the life cycle control of Leishmania. Also, recent studies suggest a fundamentally important role of RNA-binding proteins (RBPs) in regulating the downstream effects of the HSP90 inhibition in Leishmania. Phosphorylation-dephosphorylation dynamics of RBPs in higher eukaryotes serves as an important on/off switch to regulate RNA processing and decay in response to extracellular signals and cell cycle check points. In the current study, using a combination of highly sensitive TMT labeling-based quantitative proteomic MS and robust phosphoproteome enrichment, we show for the first time that HSP90 inhibition distinctively modulates global protein phosphorylation landscapes in the different life cycle stages of Leishmania, shedding light into a crucial role of the posttranslational modification in the differentiation of the parasite under HSP90 inhibition stress. We measured changes in phosphorylation of many RBPs and signaling proteins including protein kinases upon HSP90 inhibition in the therapeutically relevant amastigote stage. This work provides insights into the importance of HSP90-mediated protein cross-talks and regulation of phosphorylation in Leishmania, thus significantly expanding our knowledge of the posttranslational modification in Leishmania biology.

Activity-based protein profiling: A graphical review.

Activity-based protein profiling (ABPP) is a chemoproteomic technology that employs small chemical probes to directly interrogate protein function within complex proteomes. Since its initial application almost 25 years ago, ABPP has proven to be a powerful and versatile tool for addressing numerous challenges in drug discovery, including the development of highly selective small-molecule inhibitors, the discovery of new therapeutic targets, and the illumination of target proteins in tissues and organisms. This graphical review provides an overview of the rapid evolution of ABPP strategies, highlighting the versatility of the approach with selected examples of its successful application.

Navigating drug repurposing for Chagas disease: advances, challenges, and opportunities.

Chagas disease is a vector-borne illness caused by the protozoan parasite Trypanosoma cruzi (T. cruzi). It poses a significant public health burden, particularly in the poorest regions of Latin America. Currently, there is no available vaccine, and chemotherapy has been the traditional treatment for Chagas disease. However, the treatment options are limited to just two outdated medicines, nifurtimox and benznidazole, which have serious side effects and low efficacy, especially during the chronic phase of the disease. Collectively, this has led the World Health Organization to classify it as a neglected disease. To address this problem, new drug regimens are urgently needed. Drug repurposing, which involves the use of existing drugs already approved for the treatment of other diseases, represents an increasingly important option. This approach offers potential cost reduction in new drug discovery processes and can address pharmaceutical bottlenecks in the development of drugs for Chagas disease. In this review, we discuss the state-of-the-art of drug repurposing approaches, including combination therapy with existing drugs, to overcome the formidable challenges associated with treating Chagas disease. Organized by original therapeutic area, we describe significant recent advances, as well as the challenges in this field. In particular, we identify candidates that exhibit potential for heightened efficacy and reduced toxicity profiles with the ultimate objective of accelerating the development of new, safe, and effective treatments for Chagas disease.

Systematic study of 1,2,3-triazolyl sterols for the development of new drugs against parasitic Neglected Tropical Diseases.

A series of thirty 1,2,3-triazolylsterols, inspired by azasterols with proven antiparasitic activity, were prepared by a stereocontrolled synthesis. Ten of these compounds constitute chimeras/hybrids of 22,26-azasterol (AZA) and 1,2,3-triazolyl azasterols. The entire library was assayed against the kinetoplastid parasites Leishmania donovani, Trypanosoma cruzi, and Trypanosoma brucei, the causatives agents for visceral leishmaniasis, Chagas disease, and sleeping sickness, respectively. Most of the compounds were active at submicromolar/nanomolar concentrations with high selectivity index, when compared to their cytotoxicity against mammalian cells. Analysis of in silico physicochemical properties were conducted to rationalize the activities against the neglected tropical disease pathogens. The analogs with selective activity against L. donovani (E4, IC50 0.78 µM), T brucei (E1, IC50 0.12 µM) and T. cruzi (B1- IC50 0.33 µM), and the analogs with broad-spectrum antiparasitic activities against the three kinetoplastid parasites (B1 and B3), may be promising leads for further development as selective or broad-spectrum antiparasitic drugs.

Discovery of Leishmania Druggable Serine Proteases by Activity-Based Protein Profiling.

Leishmaniasis are a group of diseases caused by parasitic protozoa of the genus Leishmania. Current treatments are limited by difficult administration, high cost, poor efficacy, toxicity, and growing resistance. New agents, with new mechanisms of action, are urgently needed to treat the disease. Although extensively studied in other organisms, serine proteases (SPs) have not been widely explored as antileishmanial drug targets. Herein, we report for the first time an activity-based protein profiling (ABPP) strategy to investigate new therapeutic targets within the SPs of the Leishmania parasites. Active-site directed fluorophosphonate probes (rhodamine and biotin-conjugated) were used for the detection and identification of active Leishmania serine hydrolases (SHs). Significant differences were observed in the SHs expression levels throughout the Leishmania life cycle and between different Leishmania species. Using iTRAQ-labelling-based quantitative proteomic mass spectrometry, we identified two targetable SPs in Leishmania mexicana: carboxypeptidase LmxM.18.0450 and prolyl oligopeptidase LmxM.36.6750. Druggability was ascertained by selective inhibition using the commercial serine protease inhibitors chymostatin, lactacystin and ZPP, which represent templates for future anti-leishmanial drug discovery programs. Collectively, the use of ABPP method complements existing genetic methods for target identification and validation in Leishmania.

Synthesis and interaction of terminal unsaturated chemical probes with Mycobacterium tuberculosis CYP124A1.

A series of C15-C20 isoprenyl derivatives bearing terminal alkenyl and alkynyl groups were synthesized as possible substrates of the methyl-branched lipid ω-hydroxylase CYP124A1 from Mycobacterium tuberculosis. The interactions of each compound with the enzyme active site were characterized using UV-vis spectroscopy. We found that C10 and C15 analogs bind with similar affinity to the corresponding parent C10 and C15 substrates geraniol and farnesol, respectively. Three analogs (C10-ω-ene, C10-ω-yne, C15-ω-yne) interact with the proximal side of the heme iron by coordinating to the oxygen atom of the ferric heme, as judged by the appearance of typical Type-IA binding spectra. On the other hand, the C15-ω-ene analog interacts with the ferric heme by displacing the bound water that generates a typical Type I binding spectrum. We were unable to detect P450-mediated oxidation of these probes following extended incubations with CYP124A1 in our reconstituted assay system, whereas a control reaction containing farnesol was converted to ω-hydroxy farnesol under the same conditions. To understand the lack of detectable oxidation, we explored the possibility that the analogs were acting as mechanism-based inhibitors, but we were unable to detect time-dependent loss of enzymatic activity. In order to gain insight into the lack of detectable turnover or time-dependent inhibition, we examined the interaction of each compound with the CYP124A1 active site using molecular docking simulations. The docking studies revealed a binding mode where the terminal unsaturated functional groups were sequestered within the methyl-binding pocket, rather than positioned close to the heme iron for oxidation. These results aid in the design of specific inhibitors of Mtb-CYP124A1, an interesting enzyme that is implicated in the oxidation of methyl-branched lipids, including cholesterol, within a deadly human pathogen.

Repositioning Salirasib as a new antimalarial agent.

Malaria is a serious tropical disease that kills thousands of people every year, mainly in Africa, due to Plasmodium falciparum infections. Salirasib is a promising cancer drug candidate that interferes with the post-translational modification of Ras. This S-farnesyl thiosalicylate inhibits isoprenylcysteine carboxyl methyltransferase (ICMT), a validated target for cancer drug development. There is a high homology between the human and the parasite enzyme isoforms, in addition to being a druggable target. Looking to repurpose its structure as an antimalarial drug, a collection of S-substituted derivatives of thiosalicylic acid were prepared by introducing 1,2,3-triazole as a diversity entry point or by direct alkylation of the thiol. We further investigated the in vitro toxicity of FTS analogues to Plasmodium falciparum in the asexual stages and in Vero cells. An antiplasmodial activity assay was performed using a simple, high-sensitivity methodology based on nanoluciferase (NLuc)-transfected P. falciparum parasites. The results showed that some of the analogs were active at low micromolar concentration, including Salirasib. The most potent member of the series has S-farnesyl and the 1,2,3-triazole moiety substituted with phytyl. However, the compound substituted with methyl-naphthyl shows promising physicochemical and activity values. The low cytotoxicity in eukaryotic cells of the most active analogs provided good therapeutic indices, being starting-point candidates for future antimalarial drug development.

Convenient synthesis of the immunogenic glycolipid BbGL1.

A simple and efficient method to synthesize the immunogenic glycolipid BbGL1 is introduced. Two simple steps were required to obtain the desired product in good yield. First, a highly efficient glycosylation of cholesterol using galactosyl trichloroacetimidate as a donor was performed to produce cholesteryl-ß-d-galactoside. Finally, an efficient palmitoylation on the C6-OH of the galactose of the synthesized saponin using sym-collidine and acyl chloride under microwave heating that produced BbGL1 in good yield. The procedure is a convenient and cheaper alternative to the reported procedures allowing a rapid preparation of multiple analogs and conjugates.

Endocannabinoids in Caenorhabditis elegans are essential for the mobilization of cholesterol from internal reserves.

Proper cholesterol transport is crucial for the functionality of cells. In C. elegans, certain cholesterol derivatives called dafachronic acids (DAs) govern the entry into diapause. In their absence, worms form a developmentally arrested dauer larva. Thus, cholesterol transport to appropriate places for DA biosynthesis warrants the reproductive growth. Recently, we discovered a novel class of glycosphingolipids, PEGCs, required for cholesterol mobilization/transport from internal storage pools. Here, we identify other components involved in this process. We found that strains lacking polyunsaturated fatty acids (PUFAs) undergo increased dauer arrest when grown without cholesterol. This correlates with the depletion of the PUFA-derived endocannabinoids 2-arachidonoyl glycerol and anandamide. Feeding of these endocannabinoids inhibits dauer formation caused by PUFAs deficiency or impaired cholesterol trafficking (e.g. in Niemann-Pick C1 or DAF-7/TGF-ß mutants). Moreover, in parallel to PEGCs, endocannabinoids abolish the arrest induced by cholesterol depletion. These findings reveal an unsuspected function of endocannabinoids in cholesterol trafficking regulation.

A minimalistic approach to develop new anti-apicomplexa polyamines analogs.

The development of new chemical entities against the major diseases caused by parasites is highly desired. A library of thirty diamines analogs following a minimalist approach and supported by chemoinformatics tools have been prepared and evaluated against apicomplexan parasites. Different member of the series of N,N'-disubstituted aliphatic diamines shown in vitro activities at submicromolar concentrations and high levels of selectivity against Toxoplasma gondii and in chloroquine-sensitive and resistant-strains of Plasmodium falciparum. In order to demonstrate the importance of the secondary amines, ten N,N,N',N'-tetrasubstituted aliphatic diamines derivatives were synthesized being considerably less active than their disubstituted counterpart. Theoretical studies were performed to establish the electronic factors that govern the activity of the compounds.

Antitrypanosomal and antileishmanial activity of prenyl-1,2,3-triazoles.

A series of prenyl 1,2,3-triazoles were prepared from isoprenyl azides and different alkynes. The dipolar cycloaddition reaction provided exclusively primary azide products as regioisomeric mixtures that were separated by column chromatography and fully characterized. Most of the compounds displayed antiparasitic activity against Trypanosoma cruzi and Leishmania donovani. The most active compounds were assayed as potential TcCYP51 inhibitors.

Stabilization and detection of hydrophylloquinone as di-O-methyl derivative.

Phylloquinone is a redox active naphthoquinone involved in electron transport in plants. The function of this reduced form remains unclear due to its instability, which has precluded detection. Herein, a simple method that permits the stabilization of the reduced form of phylloquinone by di-O-methylation and HPLC detection is described.

Tuning the Lewis acid phenol ortho-prenylation as a molecular diversity tool.

A diversity-oriented approach for the synthesis of various structurally different prenylated alcohols from readily accessible and common precursors was developed. With varying approaches, this article describes some successful examples of a Friedel-Crafts alkylation using methoxyphenols and different prenyl alcohols (geraniol and (E,E)-farnesol). We demonstrated that just by varying the stoichiometry of the Lewis acid used, the course of the reaction can be shifted to produce the alkylated or the cyclized product. Eighteen unique products were obtained with good isolated yields by direct alkylation with or without a consecutive π-cationic cyclization.

Click chemistry decoration of amino sterols as promising strategy to developed new leishmanicidal drugs.

A series of 1,2,3-triazolylsterols was prepared from pregnenolone through reductive amination and copper(I)-catalyzed azide-alkyne cycloaddition (click chemistry). The newly generated stereocenter of the key propargylamino intermediate provided a mixture of diastereomers which were separated chromatographically, and the configuration of the R isomer was determined by X-ray crystallography. Ten triazolyl sterols were prepared, and the products and intermediates were screened in vitro against different parasites, with some compounds presenting IC50 values in the low micromolar range against Leishmania donovani.