Sodium-dependent uptake of inorganic phosphate by the intracellular malaria parasite |
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Authors: | Saliba Kevin J Martin Rowena E Bröer Angelika Henry Roselani I McCarthy C Siobhan Downie Megan J Allen Richard J W Mullin Kylie A McFadden Geoffrey I Bröer Stefan Kirk Kiaran |
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Institution: | School of Biochemistry and Molecular Biology, The Australian National University, Canberra ACT 0200, Australia. |
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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. |
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