Phospholipid Translocation andMiltefosine Potency Require Both L. donovaniMiltefosine Transporter and the New Protein LdRos3 in Leishmania Parasites*□S

The antitumor drug miltefosine has been recently approved as the first oral drug active against visceral leishmaniasis. We have previously identified the L. donovani miltefosine trans-porter (LdMT) as a P-type ATPase involved in phospholipid translocation at the plasmamembrane of Leishmania parasites. Here we show that this protein is essential but not sufficient for the phospholipid translocation activity and, thus, for the potency of the drug. Based on recent findings in yeast, we have identified the putative subunit of LdMT, named LdRos3, as another protein factor required for the translocation activity. LdRos3belongs to theCDC50/Lem3 family, proposed as likely subunits for P4-ATPases. The phenotype of LdRos3-defective parasites was identical to that of the LdMT/, including a defect in the uptake of 7-nitrobenz-2-oxa-1,3-diazol-4-yl-ami-no)-phosphatidylserine, generally considered as not affected in