The plasma membrane permease PfNT1 is essential for purine salvage in the human malaria parasite Plasmodium falciparum

doi:10.1073/pnas.0602590103

The plasma membrane permease PfNT1 is essential for purine salvage in the human malaria parasite Plasmodium falciparum

*Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, CT 06030-3301; and
^†Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, OR 97201

Edited by P. Borst, The Netherlands Cancer Institute, Amsterdam, The Netherlands, and approved April 21, 2006 (received for review March 30, 2006)

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.

Footnotes

^‡To whom correspondence should be addressed. E-mail: choukri{at}up.uchc.edu
Author contributions: K.E.B., N.S.C., B.U., and C.B.M. designed research; K.E.B., R.Z., and W.H.W. performed research; K.E.B., R.Z., W.H.W., N.S.C., B.U., and C.B.M. analyzed data; and K.E.B., R.Z., W.H.W., N.S.C., B.U., and C.B.M. wrote the paper.
Conflict of interest statement: No conflicts declared.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations:

Abbreviations:

hENT1,

human equilibrative nucleoside transporter 1;

PfNT1,

Plasmodium falciparum nucleoside transporter 1;

PPM,

parasite plasma membrane;

BSD,

blasticidin S deaminase;

TK,

thymidine kinase;

PfGat,

P. falciparum glycerol-3-phosphate acyltransferase.