Journal
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
Volume 320, Issue 2, Pages 311-317Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.bbrc.2004.05.164
Keywords
choline; transporter; membrane potential; nutrient; phospholipid
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The uptake by the intraerythrocytic malaria parasite of the phospholipid precursor choline was investigated in parasites 'isolated' from their host cells by saponin permeabilization of the erythrocyte membrane. Choline is transported across the parasite plasma membrane then phosphorylated and thereby trapped within the parasite. Choline influx was inhibited competitively by quinine. It increased with increasing extracellular pH, decreased on depolarization of the parasite plasma membrane with a protonophore or by increasing extracellular [K], and increased in response to hyperpolarization of the membrane by decreasing extracellular [K+] or by addition of the K+ channel blocker Cs+. In ATP-depleted parasites choline was taken up but not phosphorylated. Under these conditions, imposition of an inwardly negative membrane potential using the K+ ionophore valinomycin resulted in the accumulation of choline to an intracellular concentration more than 15-fold higher than the extracellular concentration. Choline influx is therefore an electrogenic process, energized by the parasite plasma membrane potential. (C) 2004 Elsevier Inc. All rights reserved.
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