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Okombo J, Fidock DA. Towards next-generation treatment options to combat Plasmodium falciparum malaria. Nat Rev Microbiol 2024:10.1038/s41579-024-01099-x. [PMID: 39367132 DOI: 10.1038/s41579-024-01099-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/23/2024] [Indexed: 10/06/2024]
Abstract
Malaria, which is caused by infection of red blood cells with Plasmodium parasites, can be fatal in non-immune individuals if left untreated. The recent approval of the pre-erythrocytic vaccines RTS, S/AS01 and R21/Matrix-M has ushered in hope of substantial reductions in mortality rates, especially when combined with other existing interventions. However, the efficacy of these vaccines is partial, and chemotherapy remains central to malaria treatment and control. For many antimalarial drugs, clinical efficacy has been compromised by the emergence of drug-resistant Plasmodium falciparum strains. Therefore, there is an urgent need for new antimalarial medicines to complement the existing first-line artemisinin-based combination therapies. In this Review, we discuss various opportunities to expand the present malaria treatment space, appraise the current antimalarial drug development pipeline and highlight examples of promising targets. We also discuss other approaches to circumvent antimalarial resistance and how potency against drug-resistant parasites could be retained.
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Affiliation(s)
- John Okombo
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY, USA
- Center for Malaria Therapeutics and Antimicrobial Resistance, Division of Infectious Diseases, Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA
| | - David A Fidock
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY, USA.
- Center for Malaria Therapeutics and Antimicrobial Resistance, Division of Infectious Diseases, Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA.
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Cabral G, Ren B, Bisio H, Otey D, Soldati-Favre D, Brown KM. Orthologs of Plasmodium ICM1 are dispensable for Ca 2+ mobilization in Toxoplasma gondii. Microbiol Spectr 2024; 12:e0122924. [PMID: 39162502 PMCID: PMC11448412 DOI: 10.1128/spectrum.01229-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2024] [Accepted: 07/03/2024] [Indexed: 08/21/2024] Open
Abstract
Apicomplexan parasites mobilize ionic calcium (Ca2+) from intracellular stores to promote microneme secretion and facilitate motile processes including gliding motility, invasion, and egress. Recently, a multipass transmembrane protein, ICM1, was found to be important for calcium mobilization in Plasmodium falciparum and P. berghei. Comparative genomics and phylogenetics have revealed putative ICM orthologs in Toxoplasma gondii and other apicomplexans. T. gondii possesses two ICM-like proteins, which we have named TgICM1-L (TGGT1_305470) and TgICM2-L (TGGT1_309910). TgICM1-L and TgICM2-L localized to undefined puncta within the parasite cytosol. TgICM1-L and TgICM2-L are individually dispensable in tachyzoites, suggesting a potential compensatory relationship between the two proteins may exist. Surprisingly, mutants lacking both TgICM1-L and TgICM2-L are fully viable, exhibiting no obvious defects in growth, microneme secretion, invasion, or egress. Furthermore, loss of TgICM1-L, TgICM2-L, or both does not impair the parasite's ability to mobilize Ca2+. These findings suggest that additional proteins may participate in Ca2+ mobilization or import in Apicomplexa, reducing the dependence on ICM-like proteins in T. gondii. Collectively, these results highlight similar yet distinct mechanisms of Ca2+ mobilization between T. gondii and Plasmodium.IMPORTANCECa2+ signaling plays a crucial role in governing apicomplexan motility; yet, the mechanisms underlying Ca2+ mobilization from intracellular stores in these parasites remain unclear. In Plasmodium, the necessity of ICM1 for Ca2+ mobilization raises the question of whether this mechanism is conserved in other apicomplexans. Investigation into the orthologs of Plasmodium ICM1 in T. gondii revealed a differing requirement for ICM proteins between the two parasites. This study suggests that T. gondii employs ICM-independent mechanisms to regulate Ca2+ homeostasis and mobilization. Proteins involved in Ca2+ signaling in apicomplexans represent promising targets for therapeutic development.
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Affiliation(s)
- Gabriel Cabral
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Bingjian Ren
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Hugo Bisio
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
- Aix-Marseille Université, Centre National de la Recherche Scientifique, Information Génomique & Structurale, Marseille, France
| | - Dawson Otey
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Dominique Soldati-Favre
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Kevin M. Brown
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
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Gilleran JA, Ashraf K, Delvillar M, Eck T, Fondekar R, Miller EB, Hutchinson A, Dong A, Seitova A, De Souza ML, Augeri D, Halabelian L, Siekierka J, Rotella DP, Gordon J, Childers WE, Grier MC, Staker BL, Roberge JY, Bhanot P. Structure-Activity Relationship of a Pyrrole Based Series of PfPKG Inhibitors as Anti-Malarials. J Med Chem 2024; 67:3467-3503. [PMID: 38372781 DOI: 10.1021/acs.jmedchem.3c01795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Controlling malaria requires new drugs against Plasmodium falciparum. The P. falciparum cGMP-dependent protein kinase (PfPKG) is a validated target whose inhibitors could block multiple steps of the parasite's life cycle. We defined the structure-activity relationship (SAR) of a pyrrole series for PfPKG inhibition. Key pharmacophores were modified to enable full exploration of chemical diversity and to gain knowledge about an ideal core scaffold. In vitro potency against recombinant PfPKG and human PKG were used to determine compound selectivity for the parasite enzyme. P. berghei sporozoites and P. falciparum asexual blood stages were used to assay multistage antiparasitic activity. Cellular specificity of compounds was evaluated using transgenic parasites expressing PfPKG carrying a substituted "gatekeeper" residue. The structure of PfPKG bound to an inhibitor was solved, and modeling using this structure together with computational tools was utilized to understand SAR and establish a rational strategy for subsequent lead optimization.
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Affiliation(s)
- John A Gilleran
- Rutgers Molecular Design and Synthesis Core, Office for Research, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, United States
| | - Kutub Ashraf
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical School, 225 Warren Street, Newark, New Jersey 07103, United States
| | - Melvin Delvillar
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical School, 225 Warren Street, Newark, New Jersey 07103, United States
| | - Tyler Eck
- Department of Chemistry and Biochemistry and Sokol Institute of Pharmaceutical Life Sciences, Montclair State University, Montclair, New Jersey 07043, United States
| | - Raheel Fondekar
- Rutgers Molecular Design and Synthesis Core, Office for Research, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, United States
- Rutgers School of Pharmacy, 160 Frelinghuysen Road, Piscataway, New Jersey 08854, United States
| | - Edward B Miller
- Schrödinger, Inc., 1540 Broadway, 24th Floor, New York, New York 10036, United States
| | - Ashley Hutchinson
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - Aiping Dong
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - Alma Seitova
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - Mariana Laureano De Souza
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical School, 225 Warren Street, Newark, New Jersey 07103, United States
| | - David Augeri
- Rutgers Molecular Design and Synthesis Core, Office for Research, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, United States
- Schrödinger, Inc., 1540 Broadway, 24th Floor, New York, New York 10036, United States
| | - Levon Halabelian
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario M5G 1L7, Canada
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - John Siekierka
- Department of Chemistry and Biochemistry and Sokol Institute of Pharmaceutical Life Sciences, Montclair State University, Montclair, New Jersey 07043, United States
| | - David P Rotella
- Department of Chemistry and Biochemistry and Sokol Institute of Pharmaceutical Life Sciences, Montclair State University, Montclair, New Jersey 07043, United States
| | - John Gordon
- Moulder Center for Drug Discovery Research, Temple University School of Pharmacy, Philadelphia, Pennsylvania 19140, United States
| | - Wayne E Childers
- Moulder Center for Drug Discovery Research, Temple University School of Pharmacy, Philadelphia, Pennsylvania 19140, United States
| | - Mark C Grier
- Rutgers Molecular Design and Synthesis Core, Office for Research, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, United States
| | - Bart L Staker
- Seattle Structural Genomics Center for Infectious Disease, Seattle, Washington 98109, United States
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, Washington 98109, United States
| | - Jacques Y Roberge
- Rutgers Molecular Design and Synthesis Core, Office for Research, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, United States
| | - Purnima Bhanot
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical School, 225 Warren Street, Newark, New Jersey 07103, United States
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Cheuka PM, Njaria P, Mayoka G, Funjika E. Emerging Drug Targets for Antimalarial Drug Discovery: Validation and Insights into Molecular Mechanisms of Function. J Med Chem 2024; 67:838-863. [PMID: 38198596 DOI: 10.1021/acs.jmedchem.3c01828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2024]
Abstract
Approximately 619,000 malaria deaths were reported in 2021, and resistance to recommended drugs, including artemisinin-combination therapies (ACTs), threatens malaria control. Treatment failure with ACTs has been found to be as high as 93% in northeastern Thailand, and parasite mutations responsible for artemisinin resistance have already been reported in some African countries. Therefore, there is an urgent need to identify alternative treatments with novel targets. In this Perspective, we discuss some promising antimalarial drug targets, including enzymes involved in proteolysis, DNA and RNA metabolism, protein synthesis, and isoprenoid metabolism. Other targets discussed are transporters, Plasmodium falciparum acetyl-coenzyme A synthetase, N-myristoyltransferase, and the cyclic guanosine monophosphate-dependent protein kinase G. We have outlined mechanistic details, where these are understood, underpinning the biological roles and hence druggability of such targets. We believe that having a clear understanding of the underlying chemical interactions is valuable to medicinal chemists in their quest to design appropriate inhibitors.
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Affiliation(s)
- Peter Mubanga Cheuka
- Department of Chemistry, School of Natural Sciences, University of Zambia, P.O. Box 32379, Lusaka 10101, Zambia
| | - Paul Njaria
- Department of Pharmacognosy and Pharmaceutical Chemistry, Kenyatta University, P.O. Box 14548-00400, Nairobi 00100, Kenya
| | - Godfrey Mayoka
- Department of Pharmacology and Pharmacognosy, School of Pharmacy, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi 00100, Kenya
| | - Evelyn Funjika
- Department of Chemistry, School of Natural Sciences, University of Zambia, P.O. Box 32379, Lusaka 10101, Zambia
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Godara P, Reddy KS, Sahu W, Naik B, Srivastava V, Das R, Mahor A, Kumar P, Giri R, Anirudh J, Tak H, Banavath HN, Bhatt TK, Goyal AK, Prusty D. Structure-based virtual screening against multiple Plasmodium falciparum kinases reveals antimalarial compounds. Mol Divers 2023:10.1007/s11030-023-10770-z. [PMID: 38127294 DOI: 10.1007/s11030-023-10770-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 11/11/2023] [Indexed: 12/23/2023]
Abstract
The continuous emergence of resistance against most frontline antimalarial drugs has led to countless deaths in malaria-endemic countries, counting 619,000 deaths in 2021, with mutation in drug targets being the sole cause. As mutation is correlated frequently with fitness cost, the likelihood of mutation emergence in multiple targets at a time is extremely low. Hence, multitargeting compounds may seem promising to address drug resistance issues with additional benefits like increased efficacy, improved safety profile, and the requirement of fewer pills compared to traditional single and combinational drugs. In this study, we attempted to use the High Throughput Virtual Screening approach to predict multitarget inhibitors against six chemically validated Plasmodium falciparum (Pf) kinases (PfPKG, PfMAP2, PfCDPK4, PfTMK, PfPK5, PfPI4K), resulting in 21 multitargeting hits. The molecular dynamic simulation of the top six complexes (Myricetin-MAP2, Quercetin-CDPK4, Myricetin-TMK, Quercetin-PKG, Salidroside-PK5, and Salidroside-PI4K) showed stable interactions. Moreover, hierarchical clustering reveals the structural divergence of the compounds from the existing antimalarials, indicating less chance of cross-resistance. Additionally, the top three hits were validated through parasite growth inhibition assays, with quercetin and myricetin exhibiting an IC50 value of 1.84 and 3.93 µM, respectively.
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Affiliation(s)
- Priya Godara
- Department of Biochemistry, School of Life Sciences, Central University of Rajasthan, NH-8, Bandarsindri, Kishangarh, Ajmer, Rajasthan, 305817, India
| | - K Sony Reddy
- School of Biotechnology, Kalinga Institute of Industrial Technology (Deemed University), Bhubaneswar, 751024, India
| | - Welka Sahu
- School of Biotechnology, Kalinga Institute of Industrial Technology (Deemed University), Bhubaneswar, 751024, India
| | - Biswajit Naik
- Department of Biochemistry, School of Life Sciences, Central University of Rajasthan, NH-8, Bandarsindri, Kishangarh, Ajmer, Rajasthan, 305817, India
| | - Varshita Srivastava
- Department of Biochemistry, School of Life Sciences, Central University of Rajasthan, NH-8, Bandarsindri, Kishangarh, Ajmer, Rajasthan, 305817, India
| | - Rusham Das
- Department of Pharmacy, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, NH-8, Bandarsindri, Kishangarh, Ajmer, Rajasthan, 305817, India
| | - Ajay Mahor
- Department of Pharmacy, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, NH-8, Bandarsindri, Kishangarh, Ajmer, Rajasthan, 305817, India
| | - Prateek Kumar
- School of Basic Sciences, Indian Institute of Technology Mandi, Kamand, India
| | - Rajanish Giri
- School of Basic Sciences, Indian Institute of Technology Mandi, Kamand, India
| | - Jivanage Anirudh
- Department of Sports Biosciences, School of Sport Sciences, Central University of Rajasthan, Ajmer, India
| | - Harshita Tak
- Department of Sports Biosciences, School of Sport Sciences, Central University of Rajasthan, Ajmer, India
| | - Hemanth Naick Banavath
- Department of Sports Biosciences, School of Sport Sciences, Central University of Rajasthan, Ajmer, India
| | - Tarun Kumar Bhatt
- Department of Biotechnology, School of Life Sciences, Central University of Rajasthan, NH-8, Bandarsindri, Kishangarh, Ajmer, Rajasthan, 305817, India
| | - Amit Kumar Goyal
- Department of Pharmacy, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, NH-8, Bandarsindri, Kishangarh, Ajmer, Rajasthan, 305817, India
| | - Dhaneswar Prusty
- Department of Biochemistry, School of Life Sciences, Central University of Rajasthan, NH-8, Bandarsindri, Kishangarh, Ajmer, Rajasthan, 305817, India.
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Tripathi H, Bhalerao P, Singh S, Arya H, Alotaibi BS, Rashid S, Hasan MR, Bhatt TK. Malaria therapeutics: are we close enough? Parasit Vectors 2023; 16:130. [PMID: 37060004 PMCID: PMC10103679 DOI: 10.1186/s13071-023-05755-8] [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: 01/06/2023] [Accepted: 03/22/2023] [Indexed: 04/16/2023] Open
Abstract
Malaria is a vector-borne parasitic disease caused by the apicomplexan protozoan parasite Plasmodium. Malaria is a significant health problem and the leading cause of socioeconomic losses in developing countries. WHO approved several antimalarials in the last 2 decades, but the growing resistance against the available drugs has worsened the scenario. Drug resistance and diversity among Plasmodium strains hinder the path of eradicating malaria leading to the use of new technologies and strategies to develop effective vaccines and drugs. A timely and accurate diagnosis is crucial for any disease, including malaria. The available diagnostic methods for malaria include microscopy, RDT, PCR, and non-invasive diagnosis. Recently, there have been several developments in detecting malaria, with improvements leading to achieving an accurate, quick, cost-effective, and non-invasive diagnostic tool for malaria. Several vaccine candidates with new methods and antigens are under investigation and moving forward to be considered for clinical trials. This article concisely reviews basic malaria biology, the parasite's life cycle, approved drugs, vaccine candidates, and available diagnostic approaches. It emphasizes new avenues of therapeutics for malaria.
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Affiliation(s)
- Himani Tripathi
- Department of Biotechnology, Central University of Rajasthan, NH-8, Bandarsindri, 305817, Rajasthan, India
| | - Preshita Bhalerao
- Department of Biotechnology, Central University of Rajasthan, NH-8, Bandarsindri, 305817, Rajasthan, India
| | - Sujeet Singh
- Department of Biotechnology, Central University of Rajasthan, NH-8, Bandarsindri, 305817, Rajasthan, India
| | - Hemant Arya
- Department of Biotechnology, Central University of Rajasthan, NH-8, Bandarsindri, 305817, Rajasthan, India.
| | - Bader Saud Alotaibi
- Department of Clinical Laboratory Science, College of Applied Medical Sciences, Alquwayiyah, Shaqra University, Riyadh, 11971, Saudi Arabia
| | - Summya Rashid
- Department of Pharmacology and Toxicology, College of Pharmacy, Prince Sattam Bin Abdulaziz University, P.O. Box 173, Al-Kharj, 11942, Saudi Arabia
| | - Mohammad Raghibul Hasan
- Department of Clinical Laboratory Science, College of Applied Medical Sciences, Alquwayiyah, Shaqra University, Riyadh, 11971, Saudi Arabia.
| | - Tarun Kumar Bhatt
- Department of Biotechnology, Central University of Rajasthan, NH-8, Bandarsindri, 305817, Rajasthan, India.
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Ong HW, Adderley J, Tobin AB, Drewry DH, Doerig C. Parasite and host kinases as targets for antimalarials. Expert Opin Ther Targets 2023; 27:151-169. [PMID: 36942408 DOI: 10.1080/14728222.2023.2185511] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023]
Abstract
INTRODUCTION The deployment of Artemisinin-based combination therapies and transmission control measures led to a decrease in the global malaria burden over the recent decades. Unfortunately, this trend is now reversing, in part due to resistance against available treatments, calling for the development of new drugs against untapped targets to prevent cross-resistance. AREAS COVERED In view of their demonstrated druggability in noninfectious diseases, protein kinases represent attractive targets. Kinase-focussed antimalarial drug discovery is facilitated by the availability of kinase-targeting scaffolds and large libraries of inhibitors, as well as high-throughput phenotypic and biochemical assays. We present an overview of validated Plasmodium kinase targets and their inhibitors, and briefly discuss the potential of host cell kinases as targets for host-directed therapy. EXPERT OPINION We propose priority research areas, including (i) diversification of Plasmodium kinase targets (at present most efforts focus on a very small number of targets); (ii) polypharmacology as an avenue to limit resistance (kinase inhibitors are highly suitable in this respect); and (iii) preemptive limitation of resistance through host-directed therapy (targeting host cell kinases that are required for parasite survival) and transmission-blocking through targeting sexual stage-specific kinases as a strategy to protect curative drugs from the spread of resistance.
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Affiliation(s)
- Han Wee Ong
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC USA
| | - Jack Adderley
- Department of Laboratory Medicine, School of Health and Biomedical Sciences, Rmit University, Bundoora VIC Australia
| | - Andrew B Tobin
- Advanced Research Centre, University of Glasgow, Glasgow, UK
| | - David H Drewry
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC USA
| | - Christian Doerig
- Department of Laboratory Medicine, School of Health and Biomedical Sciences, Rmit University, Bundoora VIC Australia
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Kanatani S, Elahi R, Kanchanabhogin S, Vartak N, Tripathi AK, Prigge ST, Sinnis P. Screening the Pathogen Box for Inhibition of Plasmodium falciparum Sporozoite Motility Reveals a Critical Role for Kinases in Transmission Stages. Antimicrob Agents Chemother 2022; 66:e0041822. [PMID: 35943271 PMCID: PMC9487509 DOI: 10.1128/aac.00418-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 07/12/2022] [Indexed: 11/20/2022] Open
Abstract
As the malaria parasite becomes resistant to every drug that we develop, the identification and development of novel drug candidates are essential. Many studies have screened compounds designed to target the clinically important blood stages. However, if we are to shrink the malaria map, new drugs that block the transmission of the parasite are needed. Sporozoites are the infective stage of the malaria parasite, transmitted to the mammalian host as mosquitoes probe for blood. Sporozoite motility is critical to their ability to exit the inoculation site and establish infection, and drug-like compounds targeting motility are effective at blocking infection in the rodent malaria model. In this study, we established a moderate-throughput motility assay for sporozoites of the human malaria parasite Plasmodium falciparum, enabling us to screen the 400 drug-like compounds from the pathogen box provided by the Medicines for Malaria Venture for their activity. Compounds exhibiting inhibitory effects on P. falciparum sporozoite motility were further assessed for transmission-blocking activity and asexual-stage growth. Five compounds had a significant inhibitory effect on P. falciparum sporozoite motility in the nanomolar range. Using membrane feeding assays, we demonstrate that four of these compounds had inhibitory activity against the transmission of P. falciparum to the mosquito. Interestingly, of the four compounds with inhibitory activity against both transmission stages, three are known kinase inhibitors. Together with a previous study that found that several of these compounds could inhibit asexual blood-stage parasite growth, our findings provide new antimalarial drug candidates that have multistage activity.
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Affiliation(s)
- Sachie Kanatani
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
- Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Rubayet Elahi
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
- Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Sukanat Kanchanabhogin
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
- Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Natasha Vartak
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
- Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Abhai K. Tripathi
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
- Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Sean T. Prigge
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
- Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Photini Sinnis
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
- Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
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Abstract
Toxoplasma motility is both activated and suppressed by 3′,5′-cyclic nucleotide signaling. Cyclic GMP (cGMP) signaling through Toxoplasma gondii protein kinase G (TgPKG) activates motility, whereas cyclic AMP (cAMP) signaling through TgPKAc1 inhibits motility. Despite their importance, it remains unclear how cGMP and cAMP levels are maintained in Toxoplasma. Phosphodiesterases (PDEs) are known to inactivate cyclic nucleotides and are highly expanded in the Toxoplasma genome. Here, we analyzed the expression and function of the 18-member TgPDE family in tachyzoites, the virulent life stage of Toxoplasma. We detected the expression of 11 of 18 TgPDEs, confirming prior expression studies. A knockdown screen of the TgPDE family revealed four TgPDEs that contribute to lytic Toxoplasma growth (TgPDE1, TgPDE2, TgPDE5, and TgPDE9). Depletion of TgPDE1 or TgPDE2 caused severe growth defects, prompting further investigation. While TgPDE1 was important for extracellular motility, TgPDE2 was important for host cell invasion, parasite replication, host cell egress, and extracellular motility. TgPDE1 displayed a plasma membrane/cytomembranous distribution, whereas TgPDE2 displayed an endoplasmic reticulum/cytomembranous distribution. Biochemical analysis of TgPDE1 and TgPDE2 purified from Toxoplasma lysates revealed that TgPDE1 hydrolyzes both cGMP and cAMP, whereas TgPDE2 was cAMP specific. Interactome studies of TgPDE1 and TgPDE2 indicated that they do not physically interact with each other or other TgPDEs but may be regulated by kinases and proteases. Our studies have identified TgPDE1 and TgPDE2 as central regulators of tachyzoite cyclic nucleotide levels and enable future studies aimed at determining how these enzymes are regulated and cooperate to control Toxoplasma motility and growth. IMPORTANCE Apicomplexan parasites require motility to actively infect host cells and cause disease. Cyclic nucleotide signaling governs apicomplexan motility, but it is unclear how cyclic nucleotide levels are maintained in these parasites. In search of novel regulators of cyclic nucleotides in the model apicomplexan Toxoplasma, we identified and characterized two catalytically active phosphodiesterases, TgPDE1 and TgPDE2, that are important for Toxoplasma’s virulent tachyzoite life cycle. Enzymes that generate, sense, or degrade cyclic nucleotides make attractive targets for therapies aimed at paralyzing and killing apicomplexan parasites.
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