title: Sodium-dependent uptake of inorganic phosphate by the intracellular malaria parasite.
abstract: As the malaria parasite, Plasmodium falciparum, grows within its host erythrocyte it induces an increase in the permeability of the erythrocyte membrane to a range of low-molecular-mass solutes, including Na+ and K+ (ref. 1). This results in a progressive increase in the concentration of Na+ in the erythrocyte cytosol. The parasite cytosol has a relatively low Na+ concentration and there is therefore a large inward Na+ gradient across the parasite plasma membrane. Here we show that the parasite exploits the Na+ electrochemical gradient to energize the uptake of inorganic phosphate (P(i)), an essential nutrient. P(i) was taken up into the intracellular parasite by a Na+-dependent transporter, with a stoichiometry of 2Na+:1P(i) and with an apparent preference for the monovalent over the divalent form of P(i). A P(i) transporter (PfPiT) belonging to the PiT family was cloned from the parasite and localized to the parasite surface. Expression of PfPiT in Xenopus oocytes resulted in Na+-dependent P(i) uptake with characteristics similar to those observed for P(i) uptake in the parasite. This study provides new insight into the significance of the malaria-parasite-induced alteration of the ionic composition of its host cell.
authors.affiliation: School of Biochemistry and Molecular Biology, The Australian National University, Canberra ACT 0200, Australia.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Saliba
authors.forename: Rowena E
authors.initials: RE
authors.lastname: Martin
authors.forename: Angelika
authors.initials: A
authors.lastname: Bröer
authors.forename: Roselani I
authors.initials: RI
authors.lastname: Henry
authors.forename: C Siobhan
authors.initials: CS
authors.lastname: McCarthy
authors.forename: Megan J
authors.initials: MJ
authors.lastname: Downie
authors.forename: Richard J W
authors.initials: RJ
authors.lastname: Allen
authors.forename: Kylie A
authors.initials: KA
authors.lastname: Mullin
authors.forename: Geoffrey I
authors.initials: GI
authors.lastname: McFadden
authors.forename: Stefan
authors.initials: S
authors.lastname: Bröer
authors.forename: Kiaran
authors.initials: K
authors.lastname: Kirk
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D004912:Erythrocytes / Q000187:drug effects / Q000469:parasitology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008288:Malaria / Q000469:parasitology*; D009865:Oocytes; D028061:Phosphate Transport Proteins / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D010802:Phylogeny; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000378:metabolism*; D012503:Saponins / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology*; D014981:Xenopus
chemical_list: D028061:Phosphate Transport Proteins; D010710:Phosphates; D012503:Saponins; D012964:Sodium