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Moreira POL, Nogueira PM, Monte-Neto RL. Next-Generation Leishmanization: Revisiting Molecular Targets for Selecting Genetically Engineered Live-Attenuated Leishmania. Microorganisms 2023; 11:microorganisms11041043. [PMID: 37110466 PMCID: PMC10145799 DOI: 10.3390/microorganisms11041043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Revised: 04/07/2023] [Accepted: 04/14/2023] [Indexed: 04/29/2023] Open
Abstract
Despite decades of research devoted to finding a vaccine against leishmaniasis, we are still lacking a safe and effective vaccine for humans. Given this scenario, the search for a new prophylaxis alternative for controlling leishmaniasis should be a global priority. Inspired by leishmanization-a first generation vaccine strategy where live L. major parasites are inoculated in the skin to protect against reinfection-live-attenuated Leishmania vaccine candidates are promising alternatives due to their robust elicited protective immune response. In addition, they do not cause disease and could provide long-term protection upon challenge with a virulent strain. The discovery of a precise and easy way to perform CRISPR/Cas-based gene editing allowed the selection of safer null mutant live-attenuated Leishmania parasites obtained by gene disruption. Here, we revisited molecular targets associated with the selection of live-attenuated vaccinal strains, discussing their function, their limiting factors and the ideal candidate for the next generation of genetically engineered live-attenuated Leishmania vaccines to control leishmaniasis.
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Affiliation(s)
- Paulo O L Moreira
- Biotechnology Applied to Pathogens (BAP), Instituto René Rachou, Fundação Oswaldo Cruz, Fiocruz Minas, Belo Horizonte 30190-009, Brazil
| | - Paula M Nogueira
- Biotechnology Applied to Pathogens (BAP), Instituto René Rachou, Fundação Oswaldo Cruz, Fiocruz Minas, Belo Horizonte 30190-009, Brazil
| | - Rubens L Monte-Neto
- Biotechnology Applied to Pathogens (BAP), Instituto René Rachou, Fundação Oswaldo Cruz, Fiocruz Minas, Belo Horizonte 30190-009, Brazil
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2
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Efstathiou A, Smirlis D. Leishmania Protein Kinases: Important Regulators of the Parasite Life Cycle and Molecular Targets for Treating Leishmaniasis. Microorganisms 2021; 9:microorganisms9040691. [PMID: 33801655 PMCID: PMC8066228 DOI: 10.3390/microorganisms9040691] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 03/21/2021] [Accepted: 03/24/2021] [Indexed: 02/07/2023] Open
Abstract
Leishmania is a protozoan parasite of the trypanosomatid family, causing a wide range of diseases with different clinical manifestations including cutaneous, mucocutaneous and visceral leishmaniasis. According to WHO, one billion people are at risk of Leishmania infection as they live in endemic areas while there are 12 million infected people worldwide. Annually, 0.9-1.6 million new infections are reported and 20-50 thousand deaths occur due to Leishmania infection. As current chemotherapy for treating leishmaniasis exhibits numerous drawbacks and due to the lack of effective human vaccine, there is an urgent need to develop new antileishmanial therapy treatment. To this end, eukaryotic protein kinases can be ideal target candidates for rational drug design against leishmaniasis. Eukaryotic protein kinases mediate signal transduction through protein phosphorylation and their inhibition is anticipated to be disease modifying as they regulate all essential processes for Leishmania viability and completion of the parasitic life cycle including cell-cycle progression, differentiation and virulence. This review highlights existing knowledge concerning the exploitation of Leishmania protein kinases as molecular targets to treat leishmaniasis and the current knowledge of their role in the biology of Leishmania spp. and in the regulation of signalling events that promote parasite survival in the insect vector or the mammalian host.
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3
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Baker N, Catta-Preta CMC, Neish R, Sadlova J, Powell B, Alves-Ferreira EVC, Geoghegan V, Carnielli JBT, Newling K, Hughes C, Vojtkova B, Anand J, Mihut A, Walrad PB, Wilson LG, Pitchford JW, Volf P, Mottram JC. Systematic functional analysis of Leishmania protein kinases identifies regulators of differentiation or survival. Nat Commun 2021; 12:1244. [PMID: 33623024 PMCID: PMC7902614 DOI: 10.1038/s41467-021-21360-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 01/13/2021] [Indexed: 01/31/2023] Open
Abstract
Differentiation between distinct stages is fundamental for the life cycle of intracellular protozoan parasites and for transmission between hosts, requiring stringent spatial and temporal regulation. Here, we apply kinome-wide gene deletion and gene tagging in Leishmania mexicana promastigotes to define protein kinases with life cycle transition roles. Whilst 162 are dispensable, 44 protein kinase genes are refractory to deletion in promastigotes and are likely core genes required for parasite replication. Phenotyping of pooled gene deletion mutants using bar-seq and projection pursuit clustering reveal functional phenotypic groups of protein kinases involved in differentiation from metacyclic promastigote to amastigote, growth and survival in macrophages and mice, colonisation of the sand fly and motility. This unbiased interrogation of protein kinase function in Leishmania allows targeted investigation of organelle-associated signalling pathways required for successful intracellular parasitism.
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Affiliation(s)
- N Baker
- York Biomedical Research Institute, University of York, York, UK
- Department of Biology, University of York, York, UK
| | - C M C Catta-Preta
- York Biomedical Research Institute, University of York, York, UK
- Department of Biology, University of York, York, UK
| | - R Neish
- York Biomedical Research Institute, University of York, York, UK
- Department of Biology, University of York, York, UK
| | - J Sadlova
- Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic
| | - B Powell
- Department of Mathematics, University of York, York, UK
| | - E V C Alves-Ferreira
- York Biomedical Research Institute, University of York, York, UK
- Department of Biology, University of York, York, UK
| | - V Geoghegan
- York Biomedical Research Institute, University of York, York, UK
- Department of Biology, University of York, York, UK
| | - J B T Carnielli
- York Biomedical Research Institute, University of York, York, UK
- Department of Biology, University of York, York, UK
| | - K Newling
- Department of Biology, University of York, York, UK
| | - C Hughes
- York Biomedical Research Institute, University of York, York, UK
- Department of Biology, University of York, York, UK
| | - B Vojtkova
- Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic
| | - J Anand
- York Biomedical Research Institute, University of York, York, UK
- Department of Biology, University of York, York, UK
| | - A Mihut
- Department of Biology, University of York, York, UK
| | - P B Walrad
- York Biomedical Research Institute, University of York, York, UK
- Department of Biology, University of York, York, UK
| | - L G Wilson
- York Biomedical Research Institute, University of York, York, UK
- Department of Physics, University of York, York, UK
| | - J W Pitchford
- Department of Biology, University of York, York, UK
- Department of Mathematics, University of York, York, UK
| | - P Volf
- Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic
| | - J C Mottram
- York Biomedical Research Institute, University of York, York, UK.
- Department of Biology, University of York, York, UK.
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Altamura F, Rajesh R, Catta-Preta CMC, Moretti NS, Cestari I. The current drug discovery landscape for trypanosomiasis and leishmaniasis: Challenges and strategies to identify drug targets. Drug Dev Res 2020; 83:225-252. [PMID: 32249457 DOI: 10.1002/ddr.21664] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 02/05/2020] [Accepted: 03/13/2020] [Indexed: 12/11/2022]
Abstract
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 prevailed 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 validate essential genes as drug targets, including genomic editing applications and in vivo imaging.
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Affiliation(s)
- Fernando Altamura
- Institute of Parasitology, McGill University, Ste Anne de Bellevue, Quebec, Canada
| | - Rishi Rajesh
- Institute of Parasitology, McGill University, Ste Anne de Bellevue, Quebec, Canada
| | | | - Nilmar S Moretti
- Departamento de Microbiologia, Imunologia e Parasitologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil
| | - Igor Cestari
- Institute of Parasitology, McGill University, Ste Anne de Bellevue, Quebec, Canada
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Cordeiro AT. NADPH Producing Enzymes as Promising Drug Targets for Chagas Disease. Curr Med Chem 2019; 26:6564-6571. [PMID: 30306853 DOI: 10.2174/0929867325666181009152844] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 09/10/2018] [Accepted: 09/19/2018] [Indexed: 11/22/2022]
Abstract
Reduced Nicotinamide Adenine Dinucleotide Phosphate (NADPH) is a cofactor used in different anabolic reactions, such as lipid and nucleic acid synthesis, and for oxidative stress defense. NADPH is essential for parasite growth and viability. In trypanosomatid parasites, NADPH is supplied by the oxidative branch of the pentose phosphate pathway and by enzymes associated with the citric acid cycle. The present article will review recent achievements that suggest glucose-6-phosphate dehydrogenase and the cytosolic isoform of the malic enzyme as promising drug targets for the discovery of new drugs against Trypanosoma cruzi and T. brucei. Topics involving an alternative strategy in accelerating T. cruzi drug-target validation and the concept of drug-target classification will also be revisited.
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Affiliation(s)
- Artur T Cordeiro
- Brazilian Bioscience National Laboratory, Brazilian Center for Research in Energy and Materials, Campinas- SP, Brazil
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Kalesh K, Denny PW. A BONCAT-iTRAQ method enables temporally resolved quantitative profiling of newly synthesised proteins in Leishmania mexicana parasites during starvation. PLoS Negl Trop Dis 2019; 13:e0007651. [PMID: 31856154 PMCID: PMC6939940 DOI: 10.1371/journal.pntd.0007651] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 01/02/2020] [Accepted: 11/20/2019] [Indexed: 11/19/2022] Open
Abstract
Adaptation to starvation is integral to the Leishmania life cycle. The parasite can survive prolonged periods of nutrient deprivation both in vitro and in vivo. The identification of parasite proteins synthesised during starvation is key to unravelling the underlying molecular mechanisms facilitating adaptation to these conditions. Additionally, as stress adaptation mechanisms in Leishmania are linked to virulence as well as infectivity, profiling of the complete repertoire of Newly Synthesised Proteins (NSPs) under starvation is important for drug target discovery. However, differential identification and quantitation of low abundance, starvation-specific NSPs from the larger background of the pre-existing parasite proteome has proven difficult, as this demands a highly selective and sensitive methodology. Herein we introduce an integrated chemical proteomics method in L. mexicana promastigotes that involves a powerful combination of the BONCAT technique and iTRAQ quantitative proteomics Mass Spectrometry (MS), which enabled temporally resolved quantitative profiling of de novo protein synthesis in the starving parasite. Uniquely, this approach integrates the high specificity of the BONCAT technique for the NSPs, with the high sensitivity and multiplexed quantitation capability of the iTRAQ proteomics MS. Proof-of-concept experiments identified over 250 starvation-responsive NSPs in the parasite. Our results show a starvation-specific increased relative abundance of several translation regulating and stress-responsive proteins in the parasite. GO analysis of the identified NSPs for Biological Process revealed translation (enrichment P value 2.47e-35) and peptide biosynthetic process (enrichment P value 4.84e-35) as extremely significantly enriched terms indicating the high specificity of the NSP towards regulation of protein synthesis. We believe that this approach will find widespread use in the study of the developmental stages of Leishmania species and in the broader field of protozoan biology. Periodic nutrient scarcity plays crucial roles in the life cycle of the protozoan parasite Leishmania spp. Although adaptation to nutrient stress has a pivotal role in Leishmania biology, the underlying mechanisms remain poorly understood. In a period of nutrient starvation, the parasite responds by decreasing its protein production to conserve nutrient resources and to prevent formation of toxic proteins. However, even during severe starvation, the parasite generates certain essential quality control and rescue proteins. Differential identification of the complete repertoire of these proteins synthesised during starvation from the pre-existing proteins in the parasite holds the key to understanding the starvation adaptation mechanisms. This has been challenging to accomplish due to technical limitations. Using a combination of chemical labelling techniques and protein mass-spectrometry, we selectively identified and measured the proteins generated in the starving Leishmania parasite. Our results show a starvation time-dependent differential expression of important protein synthesis regulators in the parasite. This will serve as an important dataset for a holistic understanding of the starvation adaptation mechanisms in Leishmania. We also believe that this method will find widespread applications in the field of protozoa and other parasites causing Neglected Tropical Diseases.
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Affiliation(s)
- Karunakaran Kalesh
- Department of Chemistry, Durham University, Durham, United Kingdom
- * E-mail:
| | - Paul W. Denny
- Department of Biosciences, Durham University, Durham, United Kingdom
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Abstract
Leishmania parasites are the causative agents of a broad spectrum of diseases. The parasites migrate between sand-fly vectors and mammalian hosts, adapting to changing environments by driving a regulated program of gene expression, with translation regulation playing a key role. The leishmanias encode six different paralogs of eIF4E, the cap-binding translation initiation factor. Since these vary in function, expression profile, and assemblage, it is assumed that each is assigned a specific role throughout the life cycle. Using the CRISPR-Cas9 system for Leishmania, we generated a null mutant of LeishIF4E1, eliminating both alleles. Although the mutant cells were viable, their morphology was altered and their ability to synthesize the flagellum was impaired. Elimination of LeishIF4E1 affected their protein expression profile and decreased their ability to infect cultured macrophages. Restoring LeishIF4E1 expression restored the affected features. This study highlights the importance of LeishIF4E1 in diverse cellular events during the life cycle of Leishmania. Leishmania parasites cycle between sand-fly vectors and mammalian hosts, adapting to changing environmental conditions by driving a stage-specific program of gene expression, which is tightly regulated by translation processes. Leishmania encodes six eIF4E orthologs (LeishIF4Es) and five eIF4G candidates, forming different cap-binding complexes with potentially varying functions. Most LeishIF4E paralogs display temperature sensitivity in their cap-binding activity, except for LeishIF4E1, which maintains its cap-binding activity under all conditions. We used the CRISPR-Cas9 system to successfully generate a null mutant of LeishIF4E1 and examine how its elimination affected parasite physiology. Although the LeishIF4E1–/– null mutant was viable, its growth was impaired, in line with a reduction in global translation. As a result of the mutation, the null LeishIF4E1–/– mutant had a defective morphology, as the cells were round and unable to grow a normal flagellum. This was further emphasized when the LeishIF4E1–/– cells failed to develop the promastigote morphology once they shifted from conditions that generate axenic amastigotes (33°C, pH 5.5) back to neutral pH and 25°C, and they maintained their short flagellum and circular structure. Finally, the LeishIF4E1–/– null mutant displayed difficulty in infecting cultured macrophages. The morphological changes and reduced infectivity of the mutant may be related to differences in the proteomic profile of LeishIF4E1–/– cells from that of controls. All defects monitored in the LeishIF4E1–/– null mutant were reversed in the add-back strain, in which expression of LeishIF4E1 was reconstituted, establishing a strong link between the cellular defects and the absence of LeishIF4E1 expression. IMPORTANCELeishmania parasites are the causative agents of a broad spectrum of diseases. The parasites migrate between sand-fly vectors and mammalian hosts, adapting to changing environments by driving a regulated program of gene expression, with translation regulation playing a key role. The leishmanias encode six different paralogs of eIF4E, the cap-binding translation initiation factor. Since these vary in function, expression profile, and assemblage, it is assumed that each is assigned a specific role throughout the life cycle. Using the CRISPR-Cas9 system for Leishmania, we generated a null mutant of LeishIF4E1, eliminating both alleles. Although the mutant cells were viable, their morphology was altered and their ability to synthesize the flagellum was impaired. Elimination of LeishIF4E1 affected their protein expression profile and decreased their ability to infect cultured macrophages. Restoring LeishIF4E1 expression restored the affected features. This study highlights the importance of LeishIF4E1 in diverse cellular events during the life cycle of Leishmania.
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Román-Carraro FC, Florencio-Martínez LE, Romero-Meza G, Nepomuceno-Mejía T, Carrero JC, Arroyo R, Ortega-López J, Manning-Cela RG, Martínez-Calvillo S. TFIIIB Subunit Bdp1 Participates in RNA Polymerase III Transcription in the Protozoan Parasite Leishmania major. BIOMED RESEARCH INTERNATIONAL 2019; 2019:1425281. [PMID: 31058184 PMCID: PMC6463643 DOI: 10.1155/2019/1425281] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2018] [Accepted: 03/13/2019] [Indexed: 01/03/2023]
Abstract
Leishmania major, a protozoan parasite that diverged early from the main eukaryotic lineage, exhibits unusual mechanisms of gene expression. Little is known in this organism about the transcription factors involved in the synthesis of tRNA, 5S rRNA, and snRNAs, transcribed by RNA Polymerase III (Pol III). Here we identify and characterize the TFIIIB subunit Bdp1 in L. major (LmBdp1). Bdp1 plays key roles in Pol III transcription initiation in other organisms, as it participates in Pol III recruitment and promoter opening. In silico analysis showed that LmBdp1 contains the typical extended SANT domain as well as other Bdp1 conserved regions. Nevertheless, LmBdp1 also displays distinctive features, including the presence of only one aromatic residue in the N-linker region. We were not able to produce null mutants of LmBdp1 by homologous recombination, as the obtained double replacement cell line contained an extra copy of LmBdp1, indicating that LmBdp1 is essential for the viability of L. major promastigotes. Notably, the mutant cell line showed reduced levels of the LmBdp1 protein, and its growth was significantly decreased in relation to wild-type cells. Nuclear run-on assays demonstrated that Pol III transcription was affected in the mutant cell line, and ChIP experiments showed that LmBdp1 binds to 5S rRNA, tRNA, and snRNA genes. Thus, our results indicate that LmBdp1 is an essential protein required for Pol III transcription in L. major.
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Affiliation(s)
- Fiordaliso C. Román-Carraro
- Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Av. de Los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Estado de México, CP 54090, Mexico
| | - Luis E. Florencio-Martínez
- Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Av. de Los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Estado de México, CP 54090, Mexico
| | - Gabriela Romero-Meza
- Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Av. de Los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Estado de México, CP 54090, Mexico
| | - Tomás Nepomuceno-Mejía
- Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Av. de Los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Estado de México, CP 54090, Mexico
| | - Julio C. Carrero
- Departamento de Inmunología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, CP 04510, Mexico
| | - Rossana Arroyo
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN 2508, Ciudad de México, CP 07360, Mexico
| | - Jaime Ortega-López
- Departamento de Biotecnología y Bioingeniería, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN 2508, Ciudad de México, CP 07360, Mexico
| | - Rebeca G. Manning-Cela
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN 2508, Ciudad de México, CP 07360, Mexico
| | - Santiago Martínez-Calvillo
- Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Av. de Los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Estado de México, CP 54090, Mexico
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Borba JV, Silva AC, Ramos PI, Grazzia N, Miguel DC, Muratov EN, Furnham N, Andrade CH. Unveiling the Kinomes of Leishmania infantum and L. braziliensis Empowers the Discovery of New Kinase Targets and Antileishmanial Compounds. Comput Struct Biotechnol J 2019; 17:352-361. [PMID: 30949306 PMCID: PMC6429582 DOI: 10.1016/j.csbj.2019.02.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 02/04/2019] [Accepted: 02/06/2019] [Indexed: 01/31/2023] Open
Abstract
Leishmaniasis is a neglected tropical disease caused by parasites of the genus Leishmania (NTD) endemic in 98 countries. Although some drugs are available, current treatments deal with issues such as toxicity, low efficacy, and emergence of resistance. Therefore, there is an urgent need to identify new targets for the development of new antileishmanial drugs. Protein kinases (PKs), which play an essential role in many biological processes, have become potential drug targets for many parasitic diseases. A refined bioinformatics pipeline was applied in order to define and compare the kinomes of L. infantum and L. braziliensis, species that cause cutaneous and visceral manifestations of leishmaniasis in the Americas, the latter being potentially fatal if untreated. Respectively, 224 and 221 PKs were identified in L. infantum and L. braziliensis overall. Almost all unclassified eukaryotic PKs were assigned to six of nine major kinase groups and, consequently, most have been classified into family and subfamily. Furthermore, revealing the kinomes for both Leishmania species allowed for the prioritization of potential drug targets that could be explored for discovering new drugs against leishmaniasis. Finally, we used a drug repurposing approach and prioritized seven approved drugs and investigational compounds to be experimentally tested against Leishmania. Trametinib and NMS-1286937 inhibited the growth of L. infantum and L. braziliensis promastigotes and amastigotes and therefore might be good candidates for the drug repurposing pipeline.
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Affiliation(s)
- Joyce V.B. Borba
- Labmol – Laboratory for Molecular Modeling and Drug Design, Faculdade de Farmácia, Universidade Federal de Goiás - UFG, Goiânia, GO, 74605-510, Brazil
| | - Arthur C. Silva
- Labmol – Laboratory for Molecular Modeling and Drug Design, Faculdade de Farmácia, Universidade Federal de Goiás - UFG, Goiânia, GO, 74605-510, Brazil
| | - Pablo I.P. Ramos
- Instituto Gonçalo Moniz (IGM), Fundação Oswaldo Cruz (FIOCRUZ), Salvador, BA, 40296-710, Brazil
| | - Nathalia Grazzia
- LEBIL – Laboratory of Leishmania Biology Infection Studies, Department of Animal Biology, Biology Institute, State University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Danilo C. Miguel
- LEBIL – Laboratory of Leishmania Biology Infection Studies, Department of Animal Biology, Biology Institute, State University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Eugene N. Muratov
- Laboratory for Molecular Modeling, Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC, 27599, USA
- Department of Chemical Technology, Odessa National Polytechnic University, Odessa, 65000, Ukraine
| | - Nicholas Furnham
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Carolina H. Andrade
- Labmol – Laboratory for Molecular Modeling and Drug Design, Faculdade de Farmácia, Universidade Federal de Goiás - UFG, Goiânia, GO, 74605-510, Brazil
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10
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Abstract
Conditional gene deletion using dimerizable Cre recombinase (DiCre) is so far the best developed system for the phenotypic analysis of essential genes in Leishmania species. Here, we describe a protocol for the generation of a conditional gene deletion mutant and the subsequent inducible deletion of a target gene. Leishmania parasites are genetically modified to express two inactive Cre subunits (DiCre) and a single LoxP-flanked version of a target gene in a context where both endogenous copies of the gene have been deleted. Treatment with rapamycin dimerizes the DiCre subunits, resulting in activation of the enzyme, recombination between the LoxP sites, and excision of the LoxP-flanked target gene. Subsequent phenotyping allows for the analysis of essential gene function.
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Duncan SM, Jones NG, Mottram JC. Recent advances in Leishmania reverse genetics: Manipulating a manipulative parasite. Mol Biochem Parasitol 2017. [DOI: 10.1016/j.molbiopara.2017.06.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Whole genome sequencing of live attenuated Leishmania donovani parasites reveals novel biomarkers of attenuation and enables product characterization. Sci Rep 2017; 7:4718. [PMID: 28680050 PMCID: PMC5498541 DOI: 10.1038/s41598-017-05088-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 06/06/2017] [Indexed: 01/03/2023] Open
Abstract
No licensed human vaccines are currently available against leishmaniasis. Several anti-leishmanial vaccines are currently undergoing testing, including genetically modified live-attenuated parasite vaccines. Studies with live attenuated Leishmania vaccines such as centrin deleted Leishmania donovani parasites (LdCen−/−) showed protective immunity in animal models. Such studies typically examined the biomarkers of protective immunity however the biomarkers of attenuation in the parasite preparations have not received adequate attention. As several candidate vaccines enter clinical trials, a more complete product characterization to enable maintenance of product quality will help meet regulatory requirements. Towards this goal, we have determined the complete genome sequence of LdCen−/− and its parent strain Ld1S-2D (LdWT) and characterized the LdCen−/− vaccine strain using bioinformatics tools. Results showed that the LdCen−/− parasites, in addition to loss of the centrin gene, have additional deletions ranging from 350 bp to 6900 bp in non-contiguous loci on several chromosomes, most commonly in untranslated regions. We have experimentally verified a subset of these adventitious deletions that had no impact on the attenuation of the LdCen−/− parasites. Our results identified hitherto unknown features of attenuation of virulence that could be used as markers of product quality in production lots and highlight the importance of product characterization in parasitic vaccines.
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Stiles JK, Hicock PI, Shah PH, Meade JC. Genomic organization, transcription, splicing and gene regulation inLeishmania. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2016. [DOI: 10.1080/00034983.1999.11813485] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Späth GF, Clos J. Joining forces: first application of a rapamycin-induced dimerizable Cre system for conditional null mutant analysis in Leishmania. Mol Microbiol 2016; 100:923-7. [PMID: 26991431 DOI: 10.1111/mmi.13374] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/15/2016] [Indexed: 11/29/2022]
Abstract
Reverse genetics in Leishmania spp has gained importance beyond basic research as efforts increase to discover and validate new drug targets. Often, the most promising targets are essential for viability of the parasites, defying a genetic analysis by current gene replacement strategies. Duncan et al. demonstrate the applicability of DiCre recombination in Leishmania for induced replacement of the kinase CRK3 gene in promastigotes. DiCre gene replacement leads to the rapid loss of the gene and allows monitoring the phenotypic effects of the loss of function, eliminating the need for prolonged cultivation and selection. Implementation of the DiCre approach will allow functional genetics of the most important of Leishmania genes and is likely to boost genetic research and drug target discovery.
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Affiliation(s)
- Gerald F Späth
- Institut Pasteur and INSERM U1201, Unité de Parasitologie Moléculaire et Signalisation, Paris, France
| | - Joachim Clos
- Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
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15
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The role of GlcNAc-PI-de-N-acetylase gene by gene knockout through homologous recombination and its consequences on survival, growth and infectivity of Leishmania major in in vitro and in vivo conditions. Acta Trop 2016; 154:63-72. [PMID: 26571069 DOI: 10.1016/j.actatropica.2015.10.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Revised: 10/18/2015] [Accepted: 10/27/2015] [Indexed: 11/20/2022]
Abstract
At present, there are no efficacious vaccines or effective drugs against leishmaniasis; therefore new and innovative control methods are urgently required. One way to achieve this important goal is through using reverse genetic engineering to evaluate important enzymes, proteins and macromolecules. One of the most important enzymes for Glycosylphosphatidylinositol (GPI) biosynthetic pathways is GlcNAc-PI-de-N-acetylase (GPI12). The molecular constructs were cloned in Escherichia coli strain Top 10 and confirmed by molecular methods and were transfected by electroporation into Leishmania major. We demonstrated that two alleles of the GPI12 gene in L. major were successfully removed and enabling the generation of a null mutant, which supports the idea that GPI12 is not an essential gene for the growth and survival of Leishmania and the homozygous knockouts of Leishmania are able to survive. We were able to produce a mutant parasite that caused no damaged to the host. Further investigations are essential to check the safety profile in laboratory animals.
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16
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Bifeld E, Chrobak M, Zander D, Schleicher U, Schönian G, Clos J. Geographical sequence variation in the Leishmania major virulence factor P46. INFECTION GENETICS AND EVOLUTION 2015; 30:195-205. [DOI: 10.1016/j.meegid.2014.12.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 12/12/2014] [Accepted: 12/24/2014] [Indexed: 01/01/2023]
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17
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Merritt C, Silva L, Tanner AL, Stuart K, Pollastri MP. Kinases as druggable targets in trypanosomatid protozoan parasites. Chem Rev 2014; 114:11280-304. [PMID: 26443079 PMCID: PMC4254031 DOI: 10.1021/cr500197d] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Indexed: 12/21/2022]
Affiliation(s)
- Christopher Merritt
- Seattle
Biomedical Research Institute, 307 Westlake Avenue North, Suite 500, Seattle, Washington 98109-5219, United States
| | - Lisseth
E. Silva
- Department
of Chemistry & Chemical Biology, Northeastern
University, 417 Egan
Research Center, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Angela L. Tanner
- Department
of Chemistry & Chemical Biology, Northeastern
University, 417 Egan
Research Center, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Kenneth Stuart
- Seattle
Biomedical Research Institute, 307 Westlake Avenue North, Suite 500, Seattle, Washington 98109-5219, United States
| | - Michael P. Pollastri
- Department
of Chemistry & Chemical Biology, Northeastern
University, 417 Egan
Research Center, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
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18
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Leprohon P, Fernandez-Prada C, Gazanion É, Monte-Neto R, Ouellette M. Drug resistance analysis by next generation sequencing in Leishmania. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2014; 5:26-35. [PMID: 25941624 PMCID: PMC4412915 DOI: 10.1016/j.ijpddr.2014.09.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 09/04/2014] [Accepted: 09/08/2014] [Indexed: 12/30/2022]
Abstract
WGS revealed the complexity of resistance which is often polyclonal in Leishmania. An impressive variation in chromosome copy numbers exist between Leishmania species. The genotype heterogeneity complicates the analysis of resistance in field isolates.
The use of next generation sequencing has the power to expedite the identification of drug resistance determinants and biomarkers and was applied successfully to drug resistance studies in Leishmania. This allowed the identification of modulation in gene expression, gene dosage alterations, changes in chromosome copy numbers and single nucleotide polymorphisms that correlated with resistance in Leishmania strains derived from the laboratory and from the field. An impressive heterogeneity at the population level was also observed, individual clones within populations often differing in both genotypes and phenotypes, hence complicating the elucidation of resistance mechanisms. This review summarizes the most recent highlights that whole genome sequencing brought to our understanding of Leishmania drug resistance and likely new directions.
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Affiliation(s)
- Philippe Leprohon
- Centre de Recherche en Infectiologie, Centre de Recherche du CHU de Québec, 2705 Laurier Blvd., Québec G1V 4G2, Canada
| | - Christopher Fernandez-Prada
- Centre de Recherche en Infectiologie, Centre de Recherche du CHU de Québec, 2705 Laurier Blvd., Québec G1V 4G2, Canada
| | - Élodie Gazanion
- Centre de Recherche en Infectiologie, Centre de Recherche du CHU de Québec, 2705 Laurier Blvd., Québec G1V 4G2, Canada
| | - Rubens Monte-Neto
- Centre de Recherche en Infectiologie, Centre de Recherche du CHU de Québec, 2705 Laurier Blvd., Québec G1V 4G2, Canada
| | - Marc Ouellette
- Centre de Recherche en Infectiologie, Centre de Recherche du CHU de Québec, 2705 Laurier Blvd., Québec G1V 4G2, Canada
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19
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Dacher M, Morales MA, Pescher P, Leclercq O, Rachidi N, Prina E, Cayla M, Descoteaux A, Späth GF. Probing druggability and biological function of essential proteins inLeishmaniacombining facilitated null mutant and plasmid shuffle analyses. Mol Microbiol 2014; 93:146-66. [DOI: 10.1111/mmi.12648] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/09/2014] [Indexed: 01/07/2023]
Affiliation(s)
- Mariko Dacher
- Institut Pasteur, CNRS URA 2581; Unité de Parasitologie moléculaire et Signalisation; Paris France
| | - Miguel A. Morales
- Institut Pasteur, CNRS URA 2581; Unité de Parasitologie moléculaire et Signalisation; Paris France
| | - Pascale Pescher
- Institut Pasteur, CNRS URA 2581; Unité de Parasitologie moléculaire et Signalisation; Paris France
| | - Olivier Leclercq
- Institut Pasteur, CNRS URA 2581; Unité de Parasitologie moléculaire et Signalisation; Paris France
| | - Najma Rachidi
- Institut Pasteur, CNRS URA 2581; Unité de Parasitologie moléculaire et Signalisation; Paris France
| | - Eric Prina
- Institut Pasteur, CNRS URA 2581; Unité de Parasitologie moléculaire et Signalisation; Paris France
| | - Mathieu Cayla
- Institut Pasteur, CNRS URA 2581; Unité de Parasitologie moléculaire et Signalisation; Paris France
| | - Albert Descoteaux
- INRS-Institut Armand-Frappier and Center for Host-Parasite Interactions; Laval Québec Canada
| | - Gerald F. Späth
- Institut Pasteur, CNRS URA 2581; Unité de Parasitologie moléculaire et Signalisation; Paris France
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20
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Singh K, Veluru NK, Trivedi V, Gupta CM, Sahasrabuddhe AA. An actin-like protein is involved in regulation of mitochondrial and flagellar functions as well as in intramacrophage survival of Leishmania donovani. Mol Microbiol 2014; 91:562-78. [PMID: 24354789 DOI: 10.1111/mmi.12477] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/01/2013] [Indexed: 11/30/2022]
Abstract
Actin-related proteins are ubiquitous actin-like proteins that show high similarity with actin in terms of their amino acid sequence and three-dimensional structure. However, in lower eukaryotes, such as trypanosomatids, their functions have not yet been explored. Here, we show that a novel actin-related protein (ORF LmjF.13.0950) is localized mainly in the Leishmania mitochondrion. We further reveal that depletion of the intracellular levels of this protein leads to an appreciable decrease in the mitochondrial membrane potential as well as in the ATP production, which appears to be accompanied with impairment in the flagellum assembly and motility. Additionally, we report that the mutants so generated fail to survive inside the mouse peritoneal macrophages. These abnormalities are, however, reversed by the episomal gene complementation. Our results, for the first time indicate that apart from their classical roles in the cytoplasm and nucleus, actin-related proteins may also regulate the mitochondrial function, and in case of Leishmania donovani they may also serve as the essential factor for their survival in the host cells.
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Affiliation(s)
- Kuldeep Singh
- Molecular and Structural Biology Division, CSIR-Central Drug Research Institute, Lucknow, PIN-226031, Uttar Pradesh, India
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21
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Williams RAM, Mottram JC, Coombs GH. Distinct roles in autophagy and importance in infectivity of the two ATG4 cysteine peptidases of Leishmania major. J Biol Chem 2012; 288:3678-90. [PMID: 23166325 PMCID: PMC3561585 DOI: 10.1074/jbc.m112.415372] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Macroautophagy in Leishmania, which is important for the cellular remodeling required during differentiation, relies upon the hydrolytic activity of two ATG4 cysteine peptidases (ATG4.1 and ATG4.2). We have investigated the individual contributions of each ATG4 to Leishmania major by generating individual gene deletion mutants (Δatg4.1 and Δatg4.2); double mutants could not be generated, indicating that ATG4 activity is required for parasite viability. Both mutants were viable as promastigotes and infected macrophages in vitro and mice, but Δatg4.2 survived poorly irrespective of infection with promastigotes or amastigotes, whereas this was the case only when promastigotes of Δatg4.1 were used. Promastigotes of Δatg4.2 but not Δatg4.1 were more susceptible than wild type promastigotes to starvation and oxidative stresses, which correlated with increased reactive oxygen species levels and oxidatively damaged proteins in the cells as well as impaired mitochondrial function. The antioxidant N-acetylcysteine reversed this phenotype, reducing both basal and induced autophagy and restoring mitochondrial function, indicating a relationship between reactive oxygen species levels and autophagy. Deletion of ATG4.2 had a more dramatic effect upon autophagy than did deletion of ATG4.1. This phenotype is consistent with a reduced efficiency in the autophagic process in Δatg4.2, possibly due to ATG4.2 having a key role in removal of ATG8 from mature autophagosomes and thus facilitating delivery to the lysosomal network. These findings show that there is a level of functional redundancy between the two ATG4s, and that ATG4.2 appears to be the more important. Moreover, the low infectivity of Δatg4.2 demonstrates that autophagy is important for the virulence of the parasite.
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Affiliation(s)
- Roderick A M Williams
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, Scotland, United Kingdom
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22
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Mannaert A, Downing T, Imamura H, Dujardin JC. Adaptive mechanisms in pathogens: universal aneuploidy in Leishmania. Trends Parasitol 2012; 28:370-6. [PMID: 22789456 DOI: 10.1016/j.pt.2012.06.003] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 06/14/2012] [Accepted: 06/14/2012] [Indexed: 02/07/2023]
Abstract
Genomic stability and maintenance of the correct chromosome number are assumed to be essential for normal development in eukaryotes. Aneuploidy is usually associated with severe abnormalities and decrease of cell fitness, but some organisms appear to rely on aneuploidy for rapid adaptation to changing environments. This phenomenon is mostly described in pathogenic fungi and cancer cells. However, recent genome studies highlight the importance of Leishmania as a new model for studies on aneuploidy. Several reports revealed extensive variation in chromosome copy number, indicating that aneuploidy is a constitutive feature of this protozoan parasite genus. Aneuploidy appears to be beneficial in organisms that are primarily asexual, unicellular, and that undergo sporadic epidemic expansions, including common pathogens as well as cancer.
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Affiliation(s)
- An Mannaert
- Unit of Molecular Parasitology, Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
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23
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Coelho AC, Boisvert S, Mukherjee A, Leprohon P, Corbeil J, Ouellette M. Multiple mutations in heterogeneous miltefosine-resistant Leishmania major population as determined by whole genome sequencing. PLoS Negl Trop Dis 2012; 6:e1512. [PMID: 22348164 PMCID: PMC3279362 DOI: 10.1371/journal.pntd.0001512] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Accepted: 12/20/2011] [Indexed: 01/11/2023] Open
Abstract
Background Miltefosine (MF) is the first oral compound used in the chemotherapy against leishmaniasis. Since the mechanism of action of this drug and the targets of MF in Leishmania are unclear, we generated in a step-by-step manner Leishmania major promastigote mutants highly resistant to MF. Two of the mutants were submitted to a short-read whole genome sequencing for identifying potential genes associated with MF resistance. Methods/Principal Findings Analysis of the genome assemblies revealed several independent point mutations in a P-type ATPase involved in phospholipid translocation. Mutations in two other proteins—pyridoxal kinase and α-adaptin like protein—were also observed in independent mutants. The role of these proteins in the MF resistance was evaluated by gene transfection and gene disruption and both the P-type ATPase and pyridoxal kinase were implicated in MF susceptibility. The study also highlighted that resistance can be highly heterogeneous at the population level with individual clones derived from this population differing both in terms of genotypes but also susceptibility phenotypes. Conclusions/Significance Whole genome sequencing was used to pinpoint known and new resistance markers associated with MF resistance in the protozoan parasite Leishmania. The study also demonstrated the polyclonal nature of a resistant population with individual cells with varying susceptibilities and genotypes. Leishmania spp. are parasitic protozoa responsible for a spectrum of diseases known as leishmaniasis. There are few drugs available for the treatment of these diseases, and miltefosine is the first oral drug used in treatment of visceral leishmaniasis, a form of the disease that can be lethal if not treated. In this study, we seek to understand the mechanism of action and identify targets of the drug by generating promastigote mutants highly resistant to miltefosine. Two independent mutants were submitted to short read whole genome sequencing. Genome analysis of these mutants has permitted us to identify point mutations in three genes (P-type ATPase, pyridoxal kinase and α-adaptin like protein) that were also present in other independent miltefosine resistant mutants. Some of the new genes identified here could be useful as potential markers for miltefosine resistance in Leishmania. Moreover, our approach has permitted us to highlight that resistance can be highly heterogeneous at the population level with individual clones derived from this population differing both in terms of genotypes but also susceptibility phenotypes. This may have practical applications while studying resistance.
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Affiliation(s)
- Adriano C. Coelho
- Centre de Recherche en Infectiologie, Université Laval, Québec, Canada
| | | | - Angana Mukherjee
- Centre de Recherche en Infectiologie, Université Laval, Québec, Canada
| | - Philippe Leprohon
- Centre de Recherche en Infectiologie, Université Laval, Québec, Canada
| | - Jacques Corbeil
- Centre de Recherche en Infectiologie, Université Laval, Québec, Canada
| | - Marc Ouellette
- Centre de Recherche en Infectiologie, Université Laval, Québec, Canada
- * E-mail:
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24
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Ogungbe IV, Singh M, Setzer WN. Antileishmanial Natural Products from Plants. BIOACTIVE NATURAL PRODUCTS 2012. [DOI: 10.1016/b978-0-444-53836-9.00027-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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25
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Mukherjee A, Langston LD, Ouellette M. Intrachromosomal tandem duplication and repeat expansion during attempts to inactivate the subtelomeric essential gene GSH1 in Leishmania. Nucleic Acids Res 2011; 39:7499-511. [PMID: 21693561 PMCID: PMC3177219 DOI: 10.1093/nar/gkr494] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Gamma-glutamylcysteine synthetase encoded by GSH1 is the rate-limiting enzyme in the biosynthesis of glutathione and trypanothione in Leishmania. Attempts to generate GSH1 null mutants by gene disruption failed in Leishmania infantum. Removal of even a single allele invariably led to the generation of an extra copy of GSH1, maintaining two intact wild-type alleles. In the second and even third round of inactivation, the markers integrated at the homologous locus but always preserved two intact copies of GSH1. We probed into the mechanism of GSH1 duplication. GSH1 is subtelomeric on chromosome 18 and Southern blot analysis indicated that a 10-kb fragment flanked by 466-bp direct repeated sequences was duplicated in tandem on the same chromosomal allele each time GSH1 was targeted. Polymerase chain reaction analysis and sequencing confirmed the generation of novel junctions created at the level of the 466-bp repeats consequent to locus duplication. In loss of heterozygosity attempts, the same repeated sequences were utilized for generating extrachromosomal circular amplicons. Our results are consistent with break-induced replication as a mechanism for the generation of this regional polyploidy to compensate for the inactivation of an essential gene. This chromosomal repeat expansion through repeated sequences could be implicated in locus duplication in Leishmania.
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Affiliation(s)
- Angana Mukherjee
- Département de Microbiologie, Immunologie and Infectiologie, Université Laval, Québec, Canada
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26
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Engels K, Beyer C, Suárez Fernández ML, Bender F, Gassel M, Unden G, Marhöfer RJ, Mottram JC, Selzer PM. Inhibition of Eimeria tenella CDK-related kinase 2: From target identification to lead compounds. ChemMedChem 2010; 5:1259-71. [PMID: 20575139 DOI: 10.1002/cmdc.201000157] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Apicomplexan parasites encompass several human- and animal-pathogenic protozoans such as Plasmodium falciparum, Toxoplasma gondii, and Eimeria tenella. E. tenella causes coccidiosis, a disease that afflicts chickens, leading to tremendous economic losses to the global poultry industry. The considerable increase in drug resistance makes it necessary to develop new therapeutic strategies against this parasite. Cyclin-dependent kinases (CDKs) are key molecules in cell-cycle regulation and are therefore prominent target proteins in parasitic diseases. Bioinformatics analysis revealed four potential CDK-like proteins, of which one-E. tenella CDK-related kinase 2 (EtCRK2)-has already been characterized by gene cloning and expression.1 By using the CDK-specific inhibitor flavopiridol in EtCRK2 enzyme assays and schizont maturation assays (SMA), we could chemically validate CDK-like proteins as potential drug targets. An X-ray crystal structure of human CDK2 (HsCDK2) served as a template to build protein models of EtCRK2 by comparative homology modeling. Structural differences in the ATP binding site between EtCRK2 and HsCDK2, as well as chicken CDK3, were addressed for the optimization of selective ATP-competitive inhibitors. Virtual screening and "wet-bench" high-throughput screening campaigns on large compound libraries resulted in an initial set of hit compounds. These compounds were further analyzed and characterized, leading to a set of four promising lead compounds for development as EtCRK2 inhibitors.
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Affiliation(s)
- Kristin Engels
- Intervet Innovation GmbH, Drug Discovery, Zur Propstei, Schwabenheim, Germany
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27
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Katta SS, Tammana TVS, Sahasrabuddhe AA, Bajpai VK, Gupta CM. Trafficking activity of myosin XXI is required in assembly of Leishmania flagellum. J Cell Sci 2010; 123:2035-44. [PMID: 20501700 DOI: 10.1242/jcs.064725] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Actin-based myosin motors have a pivotal role in intracellular trafficking in eukaryotic cells. The parasitic protozoan organism Leishmania expresses a novel class of myosin, myosin XXI (Myo21), which is preferentially localized at the proximal region of the flagellum. However, its function in this organism remains largely unknown. Here, we show that Myo21 interacts with actin, and its expression is dependent of the growth stage. We further reveal that depletion of Myo21 levels results in impairment of the flagellar assembly and intracellular trafficking. These defects are, however, reversed by episomal complementation. Additionally, it is shown that deletion of the Myo21 gene leads to generation of ploidy, suggesting an essential role of Myo21 in survival of Leishmania cells. Together, these results indicate that actin-dependent trafficking activity of Myo21 is essentially required during assembly of the Leishmania flagellum.
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Affiliation(s)
- Santharam S Katta
- Molecular and Structural Biology Division, Central Drug Research Institute, CSIR, Uttar Pradesh, Lucknow, India
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28
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Leishmania major: disruption of signal peptidase type I and its consequences on survival, growth and infectivity. Exp Parasitol 2010; 126:135-45. [PMID: 20417202 DOI: 10.1016/j.exppara.2010.04.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2009] [Revised: 04/09/2010] [Accepted: 04/14/2010] [Indexed: 10/19/2022]
Abstract
Leishmania major (L. major) signal peptidase type I (SPase I) is an endopeptidase encoded by a single-copy gene. In all organisms, SPase I is responsible for removing the signal peptide from secretory pre-proteins and releasing mature proteins to cellular or extra-cellular space. In this study, the role of SPase I in L. major is investigated by gene deletion using homologous recombination (HR). The null mutant of SPase I was not possible to create, suggesting that SPase I is an essential gene for parasite survival. The obtained heterozygote mutant by disrupting one allele of SPase I in L. major showed significantly reduced level of infectivity in bone marrow-derived macrophages. In addition, the heterozygote mutants are unable to cause cutaneous lesion in susceptible BALB/c mice. This is the first report showing that SPase I may have an important role in Leishmania infectivity, e.g. in differentiation and survival of amastigotes. Apparently, the SPase I expression is not essential for in vitro growth of the parasite.
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29
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Gomes FC, Ali NOM, Brown E, Walker RG, Grant KM, Mottram JC. Recombinant Leishmania mexicana CRK3:CYCA has protein kinase activity in the absence of phosphorylation on the T-loop residue Thr178. Mol Biochem Parasitol 2010; 171:89-96. [PMID: 20338198 DOI: 10.1016/j.molbiopara.2010.03.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 03/01/2010] [Accepted: 03/02/2010] [Indexed: 10/19/2022]
Abstract
The activity of cyclin-dependent kinases (CDKs), which are key regulators of the eukaryotic cell cycle, is regulated through post-translational mechanisms, including binding of a cyclin and phosphorylation. Previously studies have shown that Leishmania mexicana CRK3 is an essential CDK that is a functional homologue of human CDK1. In this study, recombinant histidine tagged L. mexicana CRK3 and the cyclin CYCA were combined in vitro to produce an active histone H1 kinase that was inhibited by the CDK inhibitors, flavopiridol and indirubin-3'-monoxime. Protein kinase activity was observed in the absence of phosphorylation of the T-loop residue Thr178, but increased 5-fold upon phosphorylation by the CDK activating kinase Civ1 of Saccharomyces cerevisiae. Seven recombinant L. major CRKs (1, 2, 3, 4, 6, 7 and 8) were also expressed and purified, none of which were active as monomers. Moreover, only CRK3 was phosphorylated by Civ1. HA-tagged CYCA expressed in L. major procyclic promastigotes was co-precipitated with CRK3 and exhibited histone H1 kinase activity. These data indicate that in Leishmania CYCA interacts with CRK3 to form an active protein kinase, confirm the conservation of the regulatory mechanisms that control CDK activity in other eukaryotes, but identifies biochemical differences to human CDK1.
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Affiliation(s)
- Felipe C Gomes
- Wellcome Trust Centre for Molecular Parasitology and Division of Infection & Immunity, Faculty of Biomedical and Life Sciences, University of Glasgow, 120 University Place, Glasgow G12 8TA, UK
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30
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Lewis MD, Llewellyn MS, Gaunt MW, Yeo M, Carrasco HJ, Miles MA. Flow cytometric analysis and microsatellite genotyping reveal extensive DNA content variation in Trypanosoma cruzi populations and expose contrasts between natural and experimental hybrids. Int J Parasitol 2009; 39:1305-17. [PMID: 19393242 PMCID: PMC2731025 DOI: 10.1016/j.ijpara.2009.04.001] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 04/03/2009] [Accepted: 04/06/2009] [Indexed: 12/05/2022]
Abstract
Trypanosoma cruzi exhibits remarkable genetic heterogeneity. This is evident at the nucleotide level but also structurally, in the form of karyotypic variation and DNA content differences between strains. Although natural populations of T. cruzi are predominantly clonal, hybrid lineages (TcIId and TcIIe) have been identified and hybridisation has been demonstrated in vitro, raising the possibility that genetic exchange may continue to shape the evolution of this pathogen. The mechanism of genetic exchange identified in the laboratory is unusual, apparently involving fusion of diploid parents followed by genome erosion. We investigated DNA content diversity in natural populations of T. cruzi in the context of its genetic subdivisions by using flow cytometric analysis and multilocus microsatellite genotyping to determine the relative DNA content and estimate the ploidy of 54 cloned isolates. The maximum difference observed was 47.5% between strain Tu18 cl2 (TcIIb) and strain C8 cl1 (TcI), which we estimated to be equivalent to ∼73 Mb of DNA. Large DNA content differences were identified within and between discrete typing units (DTUs). In particular, the mean DNA content of TcI strains was significantly less than that for TcII strains (P < 0.001). Comparisons of hybrid DTUs TcIId/IIe with corresponding parental DTUs TcIIb/IIc indicated that natural hybrids are predominantly diploid. We also measured the relative DNA content of six in vitro-generated TcI hybrid clones and their parents. In contrast to TcIId/IIe hybrid strains these experimental hybrids comprised populations of sub-tetraploid organisms with mean DNA contents 1.65–1.72 times higher than the parental organisms. The DNA contents of both parents and hybrids were shown to be relatively stable after passage through a mammalian host, heat shock or nutritional stress. The results are discussed in the context of hybridisation mechanisms in both natural and in vitro settings.
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Cavalli A, Bolognesi ML. Neglected Tropical Diseases: Multi-Target-Directed Ligands in the Search for Novel Lead Candidates against Trypanosoma and Leishmania. J Med Chem 2009; 52:7339-59. [DOI: 10.1021/jm9004835] [Citation(s) in RCA: 172] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Andrea Cavalli
- Department of Pharmaceutical Sciences, Alma Mater Studiorum, University of Bologna, Via Belmeloro 6, 40126 Bologna, Italy
- Department of Drug Discovery and Development, Italian Institute of Technology, Via Morego 30, 16163 Genova, Italy
| | - Maria Laura Bolognesi
- Department of Pharmaceutical Sciences, Alma Mater Studiorum, University of Bologna, Via Belmeloro 6, 40126 Bologna, Italy
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Sahasrabuddhe AA, Nayak RC, Gupta CM. Ancient Leishmania coronin (CRN12) is involved in microtubule remodeling during cytokinesis. J Cell Sci 2009; 122:1691-9. [DOI: 10.1242/jcs.044651] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In general, coronins play an important role in actin-based processes, and are expressed in a variety of eukaryotic cells, including Leishmania. Here, we show that Leishmania coronin preferentially distributes to the distal tip during cytokinesis, and interacts with microtubules through a microtubule-based motor, kinesin K39. We further show that reduction in coronin levels by 40-50% in heterozygous coronin mutants results in generation of bipolar cells (25-30%), specifically in the log phase, owing to unregulated growth of the corset microtubules. Further analysis of bipolar cells revealed that the main cause of generation of bipolar cell morphology is the intrusion of the persistently growing corset microtubules into the other daughter cell corset from the opposite direction. This defect in cytokinesis, however, disappears upon episomal gene complementation. Additionally, our attempts to prepare homozygous mutants were unsuccessful, as only the aneuploid cells survive the selection process. These results indicate that coronin regulates microtubule remodeling during Leishmania cytokinesis and is essentially required for survival of these parasites in culture.
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Affiliation(s)
- Amogh A. Sahasrabuddhe
- Division of Molecular and Structural Biology, Central Drug Research Institute, M.G. Marg, Lucknow 226001, India
| | - Ramesh C. Nayak
- Division of Molecular and Structural Biology, Central Drug Research Institute, M.G. Marg, Lucknow 226001, India
| | - Chhitar M. Gupta
- Division of Molecular and Structural Biology, Central Drug Research Institute, M.G. Marg, Lucknow 226001, India
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Romao S, Castro H, Sousa C, Carvalho S, Tomás AM. The cytosolic tryparedoxin of Leishmania infantum is essential for parasite survival. Int J Parasitol 2008; 39:703-11. [PMID: 19135056 DOI: 10.1016/j.ijpara.2008.11.009] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2008] [Revised: 11/05/2008] [Accepted: 11/13/2008] [Indexed: 11/28/2022]
Abstract
Leishmania infantum cytosolic tryparedoxin (LiTXN1) can be regarded as a potential candidate for drug targeting. This redox active molecule, which belongs to the thioredoxin superfamily, is one constituent of the hydroperoxide elimination cascade in L. infantum and may also be involved in other cellular processes such as DNA synthesis or host-parasite interaction. In order to validate LiTXN1 as a drug target we have employed a gene replacement strategy. We observed that substitution of both chromosomal LiTXN1 alleles was only possible upon parasite complementation with an episomal copy of the gene. Furthermore, contrary to control parasites carrying the empty vector, both the insect and the mammalian stages of L. infantum retained the episomal copy of LiTXN1 in the absence of drug pressure. These results confirm the essentiality of LiTXN1 throughout the life cycle of the parasite, namely in the disease-causing amastigote stage. In addition, the data obtained showed that disruption of one allele of this gene leads only to a 25% reduction in the expression of LiTXN1. Even though this does not affect promastigote growth and susceptibility to hydrogen peroxide, ex vivo infection assays suggest that wild-type levels of LiTXN1 are required for optimal L. infantum virulence.
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Affiliation(s)
- Susana Romao
- Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal
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Ortiz D, Sanchez MA, Pierce S, Herrmann T, Kimblin N, Archie Bouwer HG, Landfear SM. Molecular genetic analysis of purine nucleobase transport in Leishmania major. Mol Microbiol 2007; 64:1228-43. [PMID: 17542917 DOI: 10.1111/j.1365-2958.2007.05730.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Leishmania major and all other parasitic protozoa are unable to synthesize purines de novo and are therefore reliant upon uptake of preformed purines from their hosts via nucleobase and nucleoside transporters. L. major expresses two nucleobase permeases, NT3 that is a high affinity transporter for purine nucleobases and NT4 that is a low affinity transporter for adenine. nt3((-/-)) null mutant promastigotes were unable to replicate in medium containing 10 microM hypoxanthine, guanine, or xanthine and replicated slowly in 10 microM adenine due to residual low affinity uptake of that purine. The NT3 transporter mediated the uptake of the anti-leishmanial drug allopurinol, and the nt3((-/-)) mutants were resistant to killing by this drug. Expression of the NT3 permease was profoundly downregulated at the protein but not the mRNA level in stationary phase compared with logarithmic phase promastigotes. The nt4((-/-)) null mutant was quantitatively impaired in survival within murine bone marrow-derived macrophages. Extensive efforts to generate an nt3((-/-))/nt4((-/-)) dual null mutant were not successful, suggesting that one of the two nucleobase permeases must be retained for robust growth of the parasite. The phenotypes of these null mutants underscore the importance of purine nucleobase transporters in the Leishmania life cycle and pharmacology.
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Affiliation(s)
- Diana Ortiz
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR 97239, USA
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35
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Schaeffer M, de Miranda A, Mottram JC, Coombs GH. Differentiation of Leishmania major is impaired by over-expression of pyroglutamyl peptidase I. Mol Biochem Parasitol 2006; 150:318-29. [PMID: 17028008 DOI: 10.1016/j.molbiopara.2006.09.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2006] [Revised: 09/06/2006] [Accepted: 09/07/2006] [Indexed: 10/24/2022]
Abstract
Pyroglutamyl peptidases I (PPI) are cysteine peptidases of the clan CF, family C15, which hydrolyse N-terminal l-pyroglutamyl residues (l-pGlu). The l-pGlu modification is a post-transcriptional modification that confers relative aminopeptidase resistance and, in some cases, is essential to the modified peptides' biological activity. PPIs have been identified in a variety of organisms, although definitive biological functions have yet to be attributed to them. The L. major PPI was expressed in Escherichia coli as active recombinant enzyme, and shown to have biochemical properties more similar to mammalian than bacterial PPIs. The LmPPI active site catalytic triad of E101, C210, and H234 was confirmed by mutagenesis. PPI activity was detected in L. major promastigotes, and the enzyme localised to the parasite cytosol. No detectable phenotype could be observed for L. major PPI-deficient mutants, which retained infectivity to macrophages in vitro and mice. However, over-expression of the active PPI, but not inactive PPI(C210A), in L. major impaired differentiation from the procyclic promastigote to the infective metacyclic promastigote. Susceptibility to a natural l-pGlu-modified antimicrobial peptide, gomesin, was tested using the different cell lines, which were all equally susceptible. Whilst PPI is widespread through the eukaryotic kingdom, this study now suggests that the enzyme is not essential for normal eukaryotic cell function. However, PPI could be involved in regulating the action of l-pGlu-modified peptides required for differentiation of L. major.
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Affiliation(s)
- Marie Schaeffer
- Division of Infection & Immunity, Institute of Biomedical and Life Sciences and Wellcome Centre for Molecular Parasitology, Glasgow Biomedical Research Centre, University of Glasgow, Glasgow G12 8TA, Scotland, UK
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36
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MacRae JI, Obado SO, Turnock DC, Roper JR, Kierans M, Kelly JM, Ferguson MAJ. The suppression of galactose metabolism in Trypanosoma cruzi epimastigotes causes changes in cell surface molecular architecture and cell morphology. Mol Biochem Parasitol 2006; 147:126-36. [PMID: 16569451 DOI: 10.1016/j.molbiopara.2006.02.011] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Revised: 02/09/2006] [Accepted: 02/15/2006] [Indexed: 11/23/2022]
Abstract
The cell surface of the epimastigote form of Trypanosoma cruzi is covered by glycoconjugates rich in galactose. The parasite cannot take up galactose through its hexose transporter, suggesting that the epimerisation of UDP-glucose to UDP-galactose may be the parasite's only route to this sugar. The T. cruzi UDP-glucose 4'-epimerase is encoded by the TcGALE gene. We were unable to make a CL-Brener strain T. cruzi epimastigote TcGALE-/- null mutant, suggesting that the gene is essential. Two TcGALE+/- single-allele knockout clones displayed aberrant morphology and haploid deficiency with respect to galactose metabolism. The morphological phenotypes included shortened flagella, increased incidence of spheromastigotes, agglutination and a novel walnut-like appearance. The reduced supply of UDP-galactose was manifest in the two clones as a six- or nine-fold reduction in the expression of galactopyranose-containing cell surface mucins and negligible or two-fold reduction in the expression of galactofuranose-containing glycoinositolphospholipids. The major loss of mucins as opposed to glycoinositolphospholipids may indicate that the latter are more important for basic parasite survival in culture. The apparent haploid deficiency suggests that epimerase levels are close to limiting, at least in the epimastigote form, and might be exploited as a potential drug target.
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Affiliation(s)
- James I MacRae
- Division of Biological Chemistry & Molecular Microbiology, The School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom
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Vergnes B, Sereno D, Tavares J, Cordeiro-da-Silva A, Vanhille L, Madjidian-Sereno N, Depoix D, Monte-Alegre A, Ouaissi A. Targeted disruption of cytosolic SIR2 deacetylase discloses its essential role in Leishmania survival and proliferation. Gene 2005; 363:85-96. [PMID: 16236469 DOI: 10.1016/j.gene.2005.06.047] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2005] [Revised: 06/08/2005] [Accepted: 06/27/2005] [Indexed: 11/20/2022]
Abstract
Proteins of the SIR2 family are characterized by a conserved catalytic domain that exerts unique NAD-dependent deacetylase activity on histone and various other cellular substrates. Functional analyses of such proteins have been carried out in a number of prokaryotes and eukaryotes organisms but until now, none have described an essential function for any SIR2 genes. Here using genetic approach, we report that a cytosolic SIR2 homolog in Leishmania is determinant to parasite survival. L. infantum promastigote tolerates deletion of one wild-type LiSIR2 allele (LiSIR2+/-) but achievement of null chromosomal mutants (LiSIR2-/-) requires episomal rescue. Accordingly, plasmid cure shows that these parasites maintain episome even in absence of drug pressure. Though single LiSIR2 gene disruption (LiSIR2+/-) does not affect the growth of parasite in the promastigote form, axenic amastigotes display a marked reduction in their capacity to multiply in vitro inside macrophages and in vivo in Balb/c mice. Taken together these data support a stage specific requirement and/or activity of the Leishmania cytosolic SIR2 protein and reveal an unrelated essential function for the life cycle of this unicellular pathogenic organism. The lack of an effective vaccine against leishmaniasis, and the need for alternative drug treatments, makes LiSIR2 protein a new attractive therapeutic target.
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Affiliation(s)
- Baptiste Vergnes
- IRD UR008 Pathogénie des Trypanosomatidés, Institut de Recherche pour le Développement, Centre IRD de Montpellier, 911 Av. Agropolis, BP 5045, 34032, Montpellier, France
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38
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Parsons M, Worthey EA, Ward PN, Mottram JC. Comparative analysis of the kinomes of three pathogenic trypanosomatids: Leishmania major, Trypanosoma brucei and Trypanosoma cruzi. BMC Genomics 2005; 6:127. [PMID: 16164760 PMCID: PMC1266030 DOI: 10.1186/1471-2164-6-127] [Citation(s) in RCA: 273] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Accepted: 09/15/2005] [Indexed: 12/27/2022] Open
Abstract
Background The trypanosomatids Leishmania major, Trypanosoma brucei and Trypanosoma cruzi cause some of the most debilitating diseases of humankind: cutaneous leishmaniasis, African sleeping sickness, and Chagas disease. These protozoa possess complex life cycles that involve development in mammalian and insect hosts, and a tightly coordinated cell cycle ensures propagation of the highly polarized cells. However, the ways in which the parasites respond to their environment and coordinate intracellular processes are poorly understood. As a part of an effort to understand parasite signaling functions, we report the results of a genome-wide analysis of protein kinases (PKs) of these three trypanosomatids. Results Bioinformatic searches of the trypanosomatid genomes for eukaryotic PKs (ePKs) and atypical PKs (aPKs) revealed a total of 176 PKs in T. brucei, 190 in T. cruzi and 199 in L. major, most of which are orthologous across the three species. This is approximately 30% of the number in the human host and double that of the malaria parasite, Plasmodium falciparum. The representation of various groups of ePKs differs significantly as compared to humans: trypanosomatids lack receptor-linked tyrosine and tyrosine kinase-like kinases, although they do possess dual-specificity kinases. A relative expansion of the CMGC, STE and NEK groups has occurred. A large number of unique ePKs show no strong affinity to any known group. The trypanosomatids possess few ePKs with predicted transmembrane domains, suggesting that receptor ePKs are rare. Accessory Pfam domains, which are frequently present in human ePKs, are uncommon in trypanosomatid ePKs. Conclusion Trypanosomatids possess a large set of PKs, comprising approximately 2% of each genome, suggesting a key role for phosphorylation in parasite biology. Whilst it was possible to place most of the trypanosomatid ePKs into the seven established groups using bioinformatic analyses, it has not been possible to ascribe function based solely on sequence similarity. Hence the connection of stimuli to protein phosphorylation networks remains enigmatic. The presence of numerous PKs with significant sequence similarity to known drug targets, as well as a large number of unusual kinases that might represent novel targets, strongly argue for functional analysis of these molecules.
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Affiliation(s)
- Marilyn Parsons
- Seattle Biomedical Research Institute, 307 Westlake Ave. N., Seattle, WA, 98109 USA
- Department of Pathobiology, University of Washington, Seattle, WA, 98195 USA
| | - Elizabeth A Worthey
- Seattle Biomedical Research Institute, 307 Westlake Ave. N., Seattle, WA, 98109 USA
| | - Pauline N Ward
- Wellcome Centre for Molecular Parasitology, The Anderson College, University of Glasgow, Glasgow G11 6NU, UK
| | - Jeremy C Mottram
- Wellcome Centre for Molecular Parasitology, The Anderson College, University of Glasgow, Glasgow G11 6NU, UK
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39
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Naula C, Parsons M, Mottram JC. Protein kinases as drug targets in trypanosomes and Leishmania. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2005; 1754:151-9. [PMID: 16198642 PMCID: PMC1452262 DOI: 10.1016/j.bbapap.2005.08.018] [Citation(s) in RCA: 158] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Revised: 08/08/2005] [Accepted: 08/10/2005] [Indexed: 11/26/2022]
Abstract
Protein kinases represent promising drug targets for a number of human and animal diseases. The recent completion of the sequenced genomes of three human-infective trypanosomatid protozoa, Leishmania major, Trypanosoma brucei and Trypanosoma cruzi, has allowed the kinome for each parasite to be defined as 179, 156 and 171 eukaryotic protein kinases respectively, that is about one third of the human complement. The analysis revealed that the trypanosomatids lack members of the receptor-linked or cytosolic tyrosine kinase families, but have an abundance of STE and CMGC family protein kinases likely to be involved in regulating cell cycle control, differentiation and response to stress during their complex life-cycles. In this review, we examine the prospects for exploiting differences between parasite and mammalian protein kinases to develop novel anti-parasitic chemotherapeutic agents.
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Affiliation(s)
- Christina Naula
- Wellcome Centre for Molecular Parasitology, The Anderson College, 56 Dumbarton Road, University of Glasgow, Glasgow G11 6NU, UK
| | - Marilyn Parsons
- Seattle Biomedical Research Institute, 307 Westlake Ave. N., Seattle, WA, 98109 USA
- Department of Pathobiology, University of Washington, Seattle, WA, 98195 USA
| | - Jeremy C. Mottram
- Wellcome Centre for Molecular Parasitology, The Anderson College, 56 Dumbarton Road, University of Glasgow, Glasgow G11 6NU, UK
- *Corresponding author:
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Martínez-Calvillo S, Stuart K, Myler PJ. Ploidy changes associated with disruption of two adjacent genes on Leishmania major chromosome 1. Int J Parasitol 2005; 35:419-29. [PMID: 15777918 DOI: 10.1016/j.ijpara.2004.12.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2004] [Revised: 12/24/2004] [Accepted: 12/24/2004] [Indexed: 11/29/2022]
Abstract
Leishmania major Friedlin (LmjF) is a kinetoplastid protozoan whose genomic sequence has been recently elucidated. About 60% of the identified genes do not have a known function, and many are trypanosomatid-specific. Here we characterise two adjacent genes from LmjF chromosome 1 (chr1): LmjF01.0750, which encodes a predicted protein with a serine/threonine protein kinase motif and LmjF01.0760, which encodes a product with no similarity to other known proteins. Orthologues of both genes are present in Trypanosoma cruzi, but neither occur in Trypanosoma brucei. We have mapped polyadenylation and spliced-leader acceptor sites for both genes, and show that they differ between Leishmania species. Attempts to generate null mutants of LmjF01.0750 by homologous recombination were unsuccessful and led to the apparent triploidy of the entire genome, suggesting that it is an essential gene. Interestingly, at least two copies of LmjF01.0750 are required for cell survival. Further evidence of genome plasticity in Leishmania was provided by changes in chr1 copy number that occurred during in vitro growth of wild-type LmjF promastigotes and following replacement of a single copy of LmjF01.0760.
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Genest PA, ter Riet B, Dumas C, Papadopoulou B, van Luenen HGAM, Borst P. Formation of linear inverted repeat amplicons following targeting of an essential gene in Leishmania. Nucleic Acids Res 2005; 33:1699-709. [PMID: 15781496 PMCID: PMC1069007 DOI: 10.1093/nar/gki304] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Attempts to inactivate an essential gene in the protozoan parasite Leishmania have often led to the generation of extra copies of the wild-type alleles of the gene. In experiments with Leishmania tarentolae set up to disrupt the gene encoding the J-binding protein 1 (JBP1), a protein binding to the unusual base beta-D-glucosyl-hydroxymethyluracil (J) of Leishmania, we obtained JBP1 mutants containing linear DNA elements (amplicons) of approximately 100 kb. These amplicons consist of a long inverted repeat with telomeric repeats at both ends and contain either the two different targeting cassettes used to inactivate JBP1, or one cassette and one JBP1 gene. Each long repeat within the linear amplicons corresponds to sequences covering the JBP1 locus, starting at the telomeres upstream of JBP1 and ending in a approximately 220 bp sequence repeated in an inverted (palindromic) orientation downstream of the JBP1 locus. We propose that these amplicons have arisen by a template switch inside a DNA replication fork involving the inverted DNA repeats and helped by the gene targeting.
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Affiliation(s)
| | | | - Carole Dumas
- Faculty of Medicine, Department of Medical Biology, Laval University, Infectious Disease Research Center, RC709, CHUL Research Center (CHUQ)2705 blvd Laurier, Quebec, Canada G1V 4G2
| | - Barbara Papadopoulou
- Faculty of Medicine, Department of Medical Biology, Laval University, Infectious Disease Research Center, RC709, CHUL Research Center (CHUQ)2705 blvd Laurier, Quebec, Canada G1V 4G2
| | | | - Piet Borst
- To whom correspondence should be addressed. Tel: +31 020 512 2880; Fax: +31 020 669 1383;
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42
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Tu X, Wang CC. Coupling of posterior cytoskeletal morphogenesis to the G1/S transition in the Trypanosoma brucei cell cycle. Mol Biol Cell 2004; 16:97-105. [PMID: 15525678 PMCID: PMC539155 DOI: 10.1091/mbc.e04-05-0368] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The expression levels of four Cdc2-related kinases (CRK1, 2, 4, and 6) in the procyclic form of Trypanosoma brucei were knocked down in pairs using the RNA interference (RNAi) technique. A double knockdown of CRK1 and CRK2 resulted in arrested cell growth in the G1 phase accompanied by an apparent cessation of nuclear DNA synthesis. The arrested cells became elongated at the posterior end like the G1-phase cells generated by knockdown of CycE1/CYC2 in a previous study. However, approximately 5% of the G1 cells in the current study also possessed multiply branched posterior ends, which have not previously been observed in T. brucei. DAPI and immunofluorescence staining showed a single nucleus, kinetoplast, basal body, and flagellum in the anterior portion of each G1 cell. The split and grossly extended posterior ends were heavily stained with antibodies to tyrosinated alpha-tubulin, suggesting an accumulation of newly synthesized microtubules. A significant population of anucleate cells (zoids), apparently derived from kinetoplast-dictated cytokinesis and cell division of the G1 cells, also had extended and branched posterior ends filled with newly synthesized microtubules. This continued posterior extension of microtubules in the G1 cells and zoids suggests that CRK1 and CRK2 exert a coordinated control on G1/S passage and the limited growth of the microtubule corset toward the posterior end. This connection may provide a new insight into the mechanism of morphological maintenance of an ancient protist during its cell cycle progression.
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Affiliation(s)
- Xiaoming Tu
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143-2280, USA
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43
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Bhuyan PK, Karikò K, Capodici J, Lubinski J, Hook LM, Friedman HM, Weissman D. Short interfering RNA-mediated inhibition of herpes simplex virus type 1 gene expression and function during infection of human keratinocytes. J Virol 2004; 78:10276-81. [PMID: 15367593 PMCID: PMC516413 DOI: 10.1128/jvi.78.19.10276-10281.2004] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
RNA interference (RNAi) is an antiviral mechanism that is activated when double-stranded RNA is cleaved into fragments, called short interfering RNA (siRNA), that prime an inducible gene silencing enzyme complex. We applied RNAi against a herpes simplex virus type 1 (HSV-1) gene, glycoprotein E, which mediates cell-to-cell spread and immune evasion. In an in vitro model of infection, human keratinocytes were transfected with siRNA specific for glycoprotein E and then infected with wild-type HSV-1. RNAi-mediated gene silencing reproduced the small plaque phenotype of a gE-deletion mutant virus. The specificity of gene targeting was demonstrated by flow cytometry and Northern blot analyses. Exogenous siRNA can suppress HSV-1 glycoprotein E expression and function during active infection in vitro through RNAi. This work establishes RNAi as a genetic tool for the study of HSV and provides a foundation for development of RNAi as a novel antiviral therapy.
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Affiliation(s)
- Prakash K Bhuyan
- Division of Infectious Diseases, Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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Doerig C. Protein kinases as targets for anti-parasitic chemotherapy. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2004; 1697:155-68. [PMID: 15023358 DOI: 10.1016/j.bbapap.2003.11.021] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2003] [Accepted: 11/12/2003] [Indexed: 11/19/2022]
Abstract
Parasitic protozoa infecting humans have a staggering impact on public health, especially in the developing world. Furthermore, several protozoan species are major pathogens of domestic animals and have a considerable impact on food production. In many instances, the parasites have developed resistance against available chemotherapeutic agents, making the search for alternative drugs a priority. In line with the current interest in protein kinases inhibitors as potential drugs against a variety of diseases, the possibility that protein kinases may represent targets for novel anti-parasitic agents is being explored. Research into parasite protein kinases has benefited greatly from genome and EST sequencing projects, with the genomes of a few species fully sequenced (notably that of the human malaria parasite Plasmodium falciparum) and several more under way. The overall picture that emerged from research in this area shows that the phylogenetic isolation of parasitic protozoa is reflected by atypical structural and functional properties of many of their protein kinase homologues. Likewise, evidence is emerging, which suggests that the organisation of some otherwise well-conserved signal transduction pathways is divergent in some parasitic species. The differences between protein kinases of a parasite and their homologues in its host cell suggest that specific inhibition of the former can be achieved. The development of anti-parasitic drugs based on protein kinase inhibition is being pursued following two avenues: one consists of screening chemical libraries on recombinant enzymes; several protein kinases from parasitic protozoa are now available for this approach. The second approach relies on the identification of the molecular targets of kinase inhibitors which display anti-parasitic properties. This has led to promising developments in a few instances, in particular regarding PKG as a drug target against Eimeria and Toxoplasma, and purvalanol B, a purine-based CDK inhibitor which appears to affect unexpected targets in several protozoan parasites. The recent resolution of the structure of a Plasmodium protein kinase complexed with small inhibitory molecules opens the way to a rational approach towards the design of anti-parasitic drugs based on kinase inhibition.
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Affiliation(s)
- Christian Doerig
- Wellcome Centre for Molecular Parasitology, University of Glasgow, INSERM, 56 Dumbarton Road, Glasgow G11 6NU, Scotland, UK.
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45
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Tu X, Wang CC. The involvement of two cdc2-related kinases (CRKs) in Trypanosoma brucei cell cycle regulation and the distinctive stage-specific phenotypes caused by CRK3 depletion. J Biol Chem 2004; 279:20519-28. [PMID: 15010459 DOI: 10.1074/jbc.m312862200] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cyclin-dependent protein kinases are among the key regulators of eukaryotic cell cycle progression. Potential functions of the five cdc2-related kinases (CRK) in Trypanosoma brucei were analyzed using the RNA interference (RNA(i)) technique. In both the procyclic and bloodstream forms of T. brucei, CRK1 is apparently involved in controlling the G(1)/S transition, whereas CRK3 plays an important role in catalyzing cells across the G(2)/M junction. A knockdown of CRK1 caused accumulation of cells in the G(1) phase without apparent phenotypic change, whereas depletion of CRK3 enriched cells of both forms in the G(2)/M phase. However, two distinctive phenotypes were observed between the CRK3-deficient procyclic and bloodstream forms. The procyclic form has a majority of the cells containing a single enlarged nucleus plus one kinetoplast. There is also an enhanced population of anucleated cells, each containing a single kinetoplast known as the zoids (0N1K). The CRK3-depleted bloodstream form has an increased number of one nucleus-two kinetoplast cells (1N2K) and a small population containing aggregated multiple nuclei and multiple kinetoplasts. Apparently, these two forms have different mechanisms in cell cycle regulation. Although the procyclic form can be driven into cytokinesis and cell division by kinetoplast segregation without a completed mitosis, the bloodstream form cannot enter cytokinesis under the same condition. Instead, it keeps going through another G(1) phase and enters a new S phase resulting in an aggregate of multiple nuclei and multiple kinetoplasts in an undivided cell. The different leakiness in cell cycle regulation between two stage-specific forms of an organism provides an interesting and useful model for further understanding the evolution of cell cycle control among the eukaryotes.
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Affiliation(s)
- Xiaoming Tu
- Department of Pharmaceutical Chemistry, University of California-San Francisco, San Francisco, CA 94143-2280, USA
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Price HP, Menon MR, Panethymitaki C, Goulding D, McKean PG, Smith DF. Myristoyl-CoA:protein N-myristoyltransferase, an essential enzyme and potential drug target in kinetoplastid parasites. J Biol Chem 2003; 278:7206-14. [PMID: 12488459 DOI: 10.1074/jbc.m211391200] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Co-translational modification of eukaryotic proteins by N-myristoylation aids subcellular targeting and protein-protein interactions. The enzyme that catalyzes this process, N-myristoyltransferase (NMT), has been characterized in the kinetoplastid protozoan parasites, Leishmania and Trypanosoma brucei. In Leishmania major, the single copy NMT gene is constitutively expressed in all parasite stages as a 48.5-kDa protein that localizes to both membrane and cytoplasmic fractions. Leishmania NMT myristoylates the target acylated Leishmania protein, HASPA, when both are co-expressed in Escherichia coli. Gene targeting experiments have shown that NMT activity is essential for viability in Leishmania. In addition, overexpression of NMT causes gross changes in parasite morphology, including the subcellular accumulation of lipids, leading to cell death. This phenotype is more extreme than that observed in Saccharomyces cerevisiae, in which overexpression of NMT activity has no obvious effects on growth kinetics or cell morphology. RNA interference assays in T. brucei have confirmed that NMT is also an essential protein in both life cycle stages of this second kinetoplastid species, suggesting that this enzyme may be an appropriate target for the development of anti-parasitic agents.
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Affiliation(s)
- Helen P Price
- Wellcome Trust Laboratories for Molecular Parasitology, Centre for Molecular Microbiology and Infection, Department of Biological Sciences, Imperial College of Science, Technology and Medicine, London SW7 2AZ, United Kingdom
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Lecaille F, Kaleta J, Brömme D. Human and parasitic papain-like cysteine proteases: their role in physiology and pathology and recent developments in inhibitor design. Chem Rev 2002; 102:4459-88. [PMID: 12475197 DOI: 10.1021/cr0101656] [Citation(s) in RCA: 393] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Fabien Lecaille
- Mount Sinai School of Medicine, Department of Human Genetics, Fifth Avenue at 100th Street, New York, New York 10029, USA
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Khan F, Tang J, Qin CL, Kim K. Cyclin-dependent kinase TPK2 is a critical cell cycle regulator in Toxoplasma gondii. Mol Microbiol 2002; 45:321-32. [PMID: 12123447 DOI: 10.1046/j.1365-2958.2002.03026.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Apicomplexan parasite Toxoplasma gondii replicates by endodyogeny, an unusual form of binary fission. We tested the role of TPK2, a homologue of the CDC2 cyclin-dependent kinases, in cell cycle regulation. TPK2 tagged with HA epitope (TPK2-HA-wt) was expressed in mammalian cells as confirmed by Western blot analysis using HA tag and PSTAIRE antibodies. TPK2-HA-wt phosphorylated a peptide from Histone H1, proving that TPK2 is a functional kinase. TPK2-HA-wt coimmunoprecipitated with mammalian cyclins A, B1, D3 and E. Despite being a functional kinase, TPK2 did not rescue Schizosaccharomyces pombe cdc2 and Saccharomyces cerevisiae cdc28 mutant strains. Overexpression of a dominant-negative mutant of TPK2 (TPK2-HA-dn) in T. gondii tachyzoites arrested replication. FACS analysis of tachyzoites expressing TPK2-HA-dn revealed an increase in the fraction of cells in S-phase when compared with TPK2-HA-wt transfected parasites. Expression of TPK2-HA-wt did not arrest tachyzoite replication. No discernable G2 cell cycle block was evident suggesting that cell cycle checkpoints differ in T. gondii from most other eukaryotic cells. These data suggest that TPK2 executes an essential function in T. gondii cell cycle and is likely to be the T. gondii CDC2 orthologue.
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Affiliation(s)
- Farzana Khan
- Department of Medicine, Division of Infectious Diseases, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Santori MI, Laría S, Gómez EB, Espinosa I, Galanti N, Téllez-Iñón MT. Evidence for CRK3 participation in the cell division cycle of Trypanosoma cruzi. Mol Biochem Parasitol 2002; 121:225-32. [PMID: 12034456 DOI: 10.1016/s0166-6851(02)00039-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Trypanosoma cruzi CRK3 gene encodes a Cdc2p related protein kinase (CRK). To establish if it has a role in the regulation of the parasite cell cycle we studied CRK3 expression and activity throughout three life cycle stages. CRK3 from epimastigote soluble extracts interacted with p13(suc1)-beads. Endogenous CRK3 phosphorylated histone H1 and this activity was inhibited by specific CDK inhibitors: Olomoucine, Flavopiridol and Roscovitine. Flavopiridol partially inhibited the growth of T. cruzi epimastigotes at 50 nM, the lowest concentration used, but even with the highest (5 microM), cell growth was not completely arrested. CRK3 from Flavopiridol-inhibited epimastigote extracts exhibited a dose dependent inhibition of histone H1 phosphorylation. T. cruzi p13(suc1)-binding CRK displayed the same inhibition profile. This suggests that CRK3 is the enzyme responsible for the majority of the kinase activity associated with p13(suc1). CRK3 activity of hydroxyurea (HU) synchronized epimastigotes peaked in G2/M boundary while the kinase activity associated to p13(suc1)-beads increased at the same time point but remained high until late G2/M. In addition, CRK3 expression was constant during the cell cycle. This is a common pattern of CDK activity regulation. Taken together, these results support the idea that CRK3 is involved in control of the cell cycle in T. cruzi.
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Affiliation(s)
- María I Santori
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (IGEBI, CONICET) and Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Vuelta de Obligado 2490 (1428), Buenos Aires, Argentina
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Papadopoulou B, Roy G, Breton M, Kündig C, Dumas C, Fillion I, Singh AK, Olivier M, Ouellette M. Reduced infectivity of a Leishmania donovani biopterin transporter genetic mutant and its use as an attenuated strain for vaccination. Infect Immun 2002; 70:62-8. [PMID: 11748164 PMCID: PMC127620 DOI: 10.1128/iai.70.1.62-68.2002] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2001] [Revised: 08/27/2001] [Accepted: 10/16/2001] [Indexed: 11/20/2022] Open
Abstract
Pterins are essential for the growth of Leishmania species, and recent work has led to the isolation of the biopterin transporter BT1. In this study, we inactivated the Leishmania donovani biopterin transporter BT1 by gene disruption mediated by homologous recombination. No transport of biopterin was detected in this mutant. The L. donovani BT1 null mutant showed a much lesser capacity for inducing infection in mice than wild-type parasites and could elicit protective immunity in mice susceptible to infection against a L. donovani challenge. Splenocytes isolated from mice immunized with the BT1 null mutant parasites produced significant amounts of interferon gamma following stimulation with L. donovani promastigotes as measured by enzyme-linked immunosorbent assay and enzyme-linked immunospot assays. Overall, these results show that by genetically manipulating the pterin transport in L. donovani, it is possible to generate an attenuated organism that could be part of a vaccination strategy.
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Affiliation(s)
- Barbara Papadopoulou
- Centre de Recherche en Infectiologie du Centre de Recherche du CHUL and Division de Microbiologie, Faculté de Médecine, Université Laval, Québec, Canada
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