title: A high susceptibility to redox imbalance of the transmissible stages of Plasmodium falciparum revealed with a luciferase-based mature gametocyte assay.
abstract: The goal to prevent Plasmodium falciparum transmission from humans to mosquitoes requires the identification of targetable metabolic processes in the mature (stage V) gametocytes, the sexual stages circulating in the bloodstream. This task is complicated by the apparently low metabolism of these cells, which renders them refractory to most antimalarial inhibitors and constrains the development of specific and sensitive cell-based assays. Here, we identify and functionally characterize the regulatory regions of the P. falciparum gene PF3D7_1234700, encoding a CPW-WPC protein and named here Upregulated in Late Gametocytes (ULG8), which we have leveraged to express reporter genes in mature male and female gametocytes. Using transgenic parasites containing a pfULG8-luciferase cassette, we investigated the susceptibility of stage V gametocytes to compounds specifically affecting redox metabolism. Our results reveal a high sensitivity of mature gametocytes to the glutathione reductase inhibitor and redox cycler drug methylene blue (MB). Using isobologram analysis, we find that a concomitant inhibition of the parasite enzyme glucose-6-phosphate dehydrogenase-6-phosphogluconolactonase, a key component of NADPH synthesis, potently synergizes MB activity. These data suggest that redox metabolism and detoxification activity play an unsuspected yet vital role in stage V gametocytes, rendering these cells exquisitely sensitive to decreases in NADPH concentration.
authors.affiliation: Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Siciliano
authors.affiliation: Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, USA.
authors.forename: T R
authors.initials: TR
authors.lastname: Santha Kumar
authors.affiliation: Dipartimento Farmaco, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Bona
authors.affiliation: Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Grazia
authors.initials: G
authors.lastname: Camarda
authors.affiliation: Department of Chemistry "G. Ciamician", University of Bologna, Bologna, Italy.
authors.forename: Maria Maddalena
authors.initials: MM
authors.lastname: Calabretta
authors.affiliation: Department of Chemistry "G. Ciamician", University of Bologna, Bologna, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Cevenini
authors.affiliation: European School of Chemistry, Polymers and Materials (ECPM), UMR 7509 Centre National de la Recherche Scientifique and University of Strasbourg, Strasbourg, France.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Davioud-Charvet
authors.affiliation: Biochemistry and Molecular Biology, Interdisciplinary Research Center, Justus Liebig University Giessen, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Becker
authors.affiliation: Dipartimento Farmaco, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Cara
authors.affiliation: Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, USA.|Division of Infectious Diseases, Department of Medicine, Columbia University Medical Center, New York, NY, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Fidock
authors.affiliation: Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Pietro
authors.identifier: 0000-0003-0092-9840
authors.initials: P
authors.lastname: Alano
mesh_terms: D000962:Antimalarials / Q000494:pharmacology; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism / Q000502:physiology; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism / Q000502:physiology; D008156:Luciferases; D009097:Multienzyme Complexes / Q000378:metabolism / Q000502:physiology; D010084:Oxidation-Reduction / Q000187:drug effects; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism / Q000502:physiology
chemical_list: D000962:Antimalarials; D009097:Multienzyme Complexes; C560097:glucose-6-phosphate dehydrogenase-6-phosphogluconolactonase, Plasmodium falciparum; D005954:Glucosephosphate Dehydrogenase; D008156:Luciferases; D002265:Carboxylic Ester Hydrolases; C022363:6-phosphogluconolactonase