This Article Full Text Full Text (PDF) Other Versions of this Article: AAC.00057-08v1 52/7/2346    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lisk, G. Articles by Desai, S. A. Search for Related Content PubMed PubMed Citation Articles by Lisk, G. Articles by Desai, S. A.

 Previous Article  |  Next Article 

Antimicrobial Agents and Chemotherapy, July 2008, p. 2346-2354, Vol. 52, No. 7
0066-4804/08/$08.00+0     doi:10.1128/AAC.00057-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Changes in the Plasmodial Surface Anion Channel Reduce Leupeptin Uptake and Can Confer Drug Resistance in Plasmodium falciparum-Infected Erythrocytes

Laboratory of Malaria and Vector Research,¹ Biostatistics Research Branch, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland 20892,² Howard Hughes Medical Institute, Departments of Molecular Microbiology and Medicine, Washington University, St. Louis, Missouri³

Received 14 January 2008/ Returned for modification 8 March 2008/ Accepted 19 April 2008

Cysteine protease inhibitors kill malaria parasites and are being pursued for development as antimalarial agents. Because they have multiple targets within bloodstream-stage parasites, workers have assumed that resistance to these inhibitors would not be acquired easily. In the present study, we used in vitro selection to generate a parasite resistant to growth inhibition by leupeptin, a broad-profile cysteine and serine protease inhibitor. Resistance was not associated with upregulation of cysteine protease activity, reduced leupeptin sensitivity of this activity, or expression level changes for putative cysteine or serine proteases in the parasite genome. Instead, it was associated with marked changes in the plasmodial surface anion channel (PSAC), an ion channel on infected erythrocytes that functions in nutrient and bulky organic solute uptake. Osmotic fragility measurements, electrophysiological recordings, and leupeptin uptake studies revealed selective reductions in organic solute permeability via PSAC, altered single-channel gating, and reduced inhibitor affinity. These changes yielded significantly reduced leupeptin uptake and could fully account for the acquired resistance. PSAC represents a novel route for the uptake of bulky hydrophilic compounds acting against intraerythrocytic parasite targets. Drug development based on such compounds should proceed cautiously in light of possible resistance development though the selection of PSAC mutants.

Published ahead of print on 28 April 2008.