title: The plasma membrane permease PfNT1 is essential for purine salvage in the human malaria parasite Plasmodium falciparum.
abstract: The human malaria parasite Plasmodium falciparum relies on the acquisition of host purines for its survival within human erythrocytes. Purine salvage by the parasite requires specialized transporters at the parasite plasma membrane (PPM), but the exact mechanism of purine entry into the infected erythrocyte, and the primary purine source used by the parasite, remain unknown. Here, we report that transgenic parasites lacking the PPM transporter PfNT1 (P. falciparum nucleoside transporter 1) are auxotrophic for hypoxanthine, inosine, and adenosine under physiological conditions and are viable only if these normally essential nutrients are provided at excess concentrations. Transport measurements across the PPM revealed a severe reduction in hypoxanthine uptake in the knockout, whereas adenosine and inosine transport were only partially affected. These data provide compelling evidence for a sequential pathway for exogenous purine conversion into hypoxanthine using host enzymes followed by PfNT1-mediated transport into the parasite. The phenotype of the conditionally lethal mutant establishes PfNT1 as a critical component of purine salvage in P. falciparum and validates PfNT1 as a potential therapeutic target.
authors.affiliation: Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, CT 06030-3301, USA.
authors.forename: Kamal
authors.initials: K
authors.lastname: El Bissati
authors.forename: Rachel
authors.initials: R
authors.lastname: Zufferey
authors.forename: William H
authors.initials: WH
authors.lastname: Witola
authors.forename: Nicola S
authors.initials: NS
authors.lastname: Carter
authors.forename: Buddy
authors.initials: B
authors.lastname: Ullman
authors.forename: Choukri
authors.initials: C
authors.lastname: Ben Mamoun
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D002462:Cell Membrane / Q000201:enzymology*; D003470:Culture Media / Q000737:chemistry; D004912:Erythrocytes / Q000469:parasitology; D018390:Gene Targeting; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000235:genetics; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D011687:Purines / Q000378:metabolism*
chemical_list: D003470:Culture Media; D026901:Membrane Transport Proteins; C407347:NT1 protein, Plasmodium falciparum; D015800:Protozoan Proteins; D011687:Purines