Silent Information Regulator 2 from Trypanosoma cruzi Is a Potential Target to Infection Control

Human trypanosomiasis is a neglected tropical disease caused by protozoan parasites of the genus Trypanosoma. Trypanosoma brucei is responsible for sleeping sickness, also called African trypanosomiasis, while Trypanosoma cruzi causes Chagas disease, or American trypanosomiasis. Together, these diseases are responsible for significant mortality, morbidity and lost productivity in the endemic regions. There are no vaccines and treatments rely on drugs with limited efficacy, high cost, serious side effects and long administration periods. Since these diseases affect mostly the poor, there is no economic interest in the development of new drugs by pharmaceutical companies, and hopes for new treatments rely on public initiatives, public-private partnerships or philanthropic programs. The first step in the discovery of new drugs involves the identification of active molecules as starting points for further development, by either employing whole cells or by specific molecular target screenings. Research efforts undertaken by the authors’ groups have focused on exploiting both strategies in the search for new molecules for trypanosomiasis drug discovery. In this chapter, we focus on Chagas disease and the recently uncovered potential of using sirtuins as targets for infection control

A Membrane-bound eIF2 Alpha Kinase Located in Endosomes Is Regulated by Heme and Controls Differentiation and ROS Levels in Trypanosoma cruzi

Translation initiation has been described as a key step for the control of growth and differentiation of several protozoan parasites in response to environmental changes. This occurs by the activation of protein kinases that phosphorylate the alpha subunit of the translation initiation factor 2 (eIF2 alpha), which decreases translation, and in higher eukaryotes favors the expression of stress remedial response genes. However, very little is known about the signals that activate eIF2 alpha kinases in protozoan parasites. Here, we characterized an eIF2 alpha kinase of Trypanosoma cruzi (TcK2), the agent of Chagas' disease, as a transmembrane protein located in organelles that accumulate nutrients in proliferating parasite forms. We found that heme binds specifically to the catalytic domain of the kinase, inhibiting its activity. in the absence of heme, TcK2 is activated, arresting cell growth and inducing differentiation of proliferative into infective and non-proliferative forms. Parasites lacking TcK2 lose this differentiation capacity and heme is not stored in reserve organelles, remaining in the cytosol. TcK2 null cells display growth deficiencies, accumulating hydrogen peroxide that drives the generation of reactive oxygen species. the augmented level of hydrogen peroxide occurs as a consequence of increased superoxide dismutase activity and decreased peroxide activity. These phenotypes could be reverted by the re-expression of the wild type but not of a TcK2 dead mutant. These findings indicate that heme is a key factor for the growth control and differentiation through regulation of an unusual type of eIF2 alpha kinase in T. cruzi.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Universidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol Imunol & Parasitol, São Paulo, BrazilNYU, Sch Med, Dept Pathol, New York, NY USAUniversidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol Imunol & Parasitol, São Paulo, BrazilFAPESP: 2011/51973-3FAPESP: 2009/54364-8FAPESP: 2012/09403-8FAPESP: 2011/50586-6FAPESP: 2003/12722-9FAPESP: 2012/50399-4FAPESP: 2009/52047-5CNPq: 477143/2011-3CNPq: 304359/2009-2Web of Scienc

Toxoplasma gondii chitinase induces macrophage activation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Toxoplasma gondii is an obligate intracellular protozoan parasite found worldwide that is able to chronically infect almost all vertebrate species, especially birds and mammalians. Chitinases are essential to various biological processes, and some pathogens rely on chitinases for successful parasitization. Here, we purified and characterized a chitinase from T. gondii. The enzyme, provisionally named Tg_chitinase, has a molecular mass of 13.7 kDa and exhibits a Km of 0.34 mM and a Vmax of 2.64. The optimal environmental conditions for enzymatic function were at pH 4.0 and 50 degrees C. Tg_chitinase was immunolocalized in the cytoplasm of highly virulent T. gondii RH strain tachyzoites, mainly at the apical extremity. Tg_chitinase induced macrophage activation as manifested by the production of high levels of pro-inflammatory cytokines, a pathogenic hallmark of T. gondii infection. In conclusion, to our knowledge, we describe for the first time a chitinase of T. gondii tachyzoites and provide evidence that this enzyme might influence the pathogenesis of T. gondii infection.Toxoplasma gondii is an obligate intracellular protozoan parasite found worldwide that is able to chronically infect almost all vertebrate species, especially birds and mammalians. Chitinases are essential to various biological processes, and some pathoge1012112FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNQP - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2013/10741-8]2013/10741-8SEM INFORMAÇÃOThis study was supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo (Grant number 2013/10741-8). Additional financial help was provided by Conselho Nacional de Desenvolvimento Científico e Tecnológico, and Fundação de Apoio ao Ensino, Pe

Identification of Inhibitors to trypanosoma cruzi sirtuins based on compounds developed to human enzymes

Chagas disease is an illness caused by the protozoan parasite Trypanosoma cruzi, affecting more than 7 million people in the world. Benznidazole and nifurtimox are the only drugs available for treatment and in addition to causing several side effects, are only satisfactory in the acute phase of the disease. Sirtuins are NAD+-dependent deacetylases involved in several biological processes, which have become drug target candidates in various disease settings. T. cruzi presents two sirtuins, one cytosolic (TcSir2rp1) and the latter mitochondrial (TcSir2rp3). Here, we characterized the effects of human sirtuin inhibitors against T. cruzi sirtuins as an initial approach to develop specific parasite inhibitors. We found that, of 33 compounds tested, two inhibited TcSir2rp1 (15 and 17), while other five inhibited TcSir2rp3 (8, 12, 13, 30, and 32), indicating that specific inhibitors can be devised for each one of the enzymes. Furthermore, all inhibiting compounds prevented parasite proliferation in cultured mammalian cells. When combining the most effective inhibitors with benznidazole at least two compounds, 17 and 32, demonstrated synergistic effects. Altogether, these results support the importance of exploring T. cruzi sirtuins as drug targets and provide key elements to develop specific inhibitors for these enzymes as potential targets for Chagas disease treatment

Chromatin modifications in trypanosomes due to stress

Trypanosomatids are parasites of worldwide distribution with relevant importance in human and veterinary health, which inhabit invertebrate and vertebrate hosts, such that they are exposed to large environmental variations during their life cycle. the signalling mechanisms and molecular basis that lead these parasites to adjust to such distinct conditions are beginning to be understood, and are somehow related to modifications in gene expression. Although the control of gene expression in this group of organisms happens predominantly at the post-transcriptional level, they present modifications in chromatin that has been implicated in transcription initiation, replication and DNA repair. Here, we explore the current scenario of chromatin alterations in these protozoans and how these changes affect transcription, replication and DNA repair in response to environmental modifications.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Universidade Federal de São Paulo, Dept Microbiol Immunol & Parasitol, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Microbiol Immunol & Parasitol, São Paulo, BrazilWeb of Scienc

Raising the Bar(-seq) in Leishmania genetic screens

Our understanding of regulatory factors in Leishmania differentia- tion has long been restricted by the available genetic tools, but the availability of CRISPR/Cas9 has changed the landscape forever. Recently, Baker and Catta-Preta et al. applied Cas9 editing and kinome-wide bar-seq to dissect the function of 204 kinases in the Leishmania mexicana life cycle.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CNPq: 424729/2018FAPESP: 2018/09948-

Trypanosoma cruzi

Trypanosoma cruzi is the etiological agent of American trypanosomiasis, or Chagas disease, and is transmitted mainly by blood-sucking reduviid insects in endemic countries. Metacyclic trypomastigotes released in the feces during the insect blood meal enter a mammalian host through skin wounds or mucosal membranes and invade sur- rounding cells. After cell invasion, metacyclic trypomastigotes are restrained within a parasitophorous vacuole (PV), from where they escape, transform into amastigotes, and multiply in the cytosol. Later, following binary division, amastigotes differentiate back into highly motile trypomastigotes that are released upon cell lysis. They can infect neighboring cells, migrate to different tissues, or be ingested by an insect vector. The parasites in the tissues, as- sociated with an immune response, contribute to the chronic symptoms of the disease. Reactive oxygen species (ROS), among other factors, play an important role during parasite multiplication and interstage transformation.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CNPq: 424729/2018FAPESP: 2018/09948-

Stress Induces Changes in the Phosphorylation of Trypanosoma cruzi RNA Polymerase II, Affecting Its Association with Chromatin and RNA Processing

The phosphorylation of the carboxy-terminal heptapeptide repeats of the largest subunit of RNA polymerase II (Pol II) controls several transcription-related events in eukaryotes. Trypanosomatids lack these typical repeats and display an unusual transcription control. RNA Pol II associates with the transcription site of the spliced leader (SL) RNA, which is used in the trans-splicing of all mRNAs transcribed on long polycistronic units. We found that Trypanosoma cruzi RNA Pol II associated with chromatin is highly phosphorylated. When transcription is inhibited by actinomycin D, the enzyme runs off from SL genes, remaining hyperphosphorylated and associated with polycistronic transcription units. Upon heat shock, the enzyme is dephosphorylated and remains associated with the chromatin. Transcription is partially inhibited with the accumulation of housekeeping precursor mRNAs, except for heat shock genes. DNA damage caused dephosphorylation and transcription arrest, with RNA Pol II dissociating from chromatin although staying at the SL. in the presence of calyculin A, the hyperphosphorylated form detached from chromatin, including the SL loci. These results indicate that in trypanosomes, the unusual RNA Pol II is phosphorylated during the transcription of SL and polycistronic operons. Different types of stresses modify its phosphorylation state, affecting pre-RNA processing

Chemogenetic characterization of inositol phosphate metabolic pathway reveals druggable enzymes for targeting kinetoplastid parasites

Kinetoplastids cause Chagas disease, human Afri- can trypanosomiasis, and leishmaniases. Current treatments for these diseases are toxic and ineffi- cient, and our limited knowledge of drug targets and inhibitors has dramatically hindered the devel- opment of new drugs. Here we used a chemogenetic approach to identify new kinetoplastid drug targets and inhibitors. We conditionally knocked down Try- panosoma brucei inositol phosphate (IP) pathway genes and showed that almost every pathway step is essential for parasite growth and infection. Using a genetic and chemical screen, we identified inhibi- tors that target IP pathway enzymes and are selec- tive against T. brucei. Two series of these inhibitors acted on T. brucei inositol polyphosphate multiki- nase (IPMK) preventing Ins(1,4,5)P3 and Ins(1,3,4,5) P4 phosphorylation. We show that IPMK is function- ally conserved among kinetoplastids and that its inhi- bition is also lethal for Trypanosoma cruzi. Hence, IP enzymes are viable drug targets in kinetoplastids, and IPMK inhibitors may aid the development of new drugs.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP: 2012/09403-8; 2013/20074-

The current drug discovery landscape for trypanosomiasis and leishmaniasis: challenges and strategies to identify drug targets

Human trypanosomiasis and leishmaniasis are vector-borne neglected tropical diseases caused by infection with the protozoan parasites Trypanosoma spp. and Leishmania spp., respectively. Once restricted to endemic areas, these diseases are now distributed worldwide due to human migration, climate change, and anthropogenic disturbance, causing significant health and economic burden globally. The current chemotherapy used to treat these diseases has limited efficacy, and drug resistance is spreading. Hence, new drugs are urgently needed. Phenotypic compound screenings have pre- vailed as the leading method to discover new drug candidates against these diseases. However, the publication of the complete genome sequences of multiple strains, advances in the application of CRISPR/Cas9 technology, and in vivo bioluminescence- based imaging have set the stage for advancing target-based drug discovery. This review analyses the limitations of the narrow pool of available drugs presently used for treating these diseases. It describes the current drug-based clinical trials highlighting the most promising leads. Furthermore, the review presents a focused discussion on the most important biological and pharmacological challenges that target-based drug discovery programs must overcome to advance drug candidates. Finally, it examines the advantages and limitations of modern research tools designed to identify and vali- date essential genes as drug targets, including genomic editing applications and in vivo imaging.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP: 2018/09948-