RT Journal Article
SR Electronic
T1 Substrate and inhibitor specificity of the Plasmodium berghei Equilibrative Nucleoside Transporter Type 1 (PbENT1)
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP mol.115.101386
DO 10.1124/mol.115.101386
A1 Avish Arora
A1 Roman Deniskin
A1 Yvett Sosa
A1 Sita Nirupama Nishtala
A1 Philipp P. Henrich
A1 T.R. Santha Kumar
A1 David A. Fidock
A1 Myles H. Akabas
YR 2016
UL http://molpharm.aspetjournals.org/content/early/2016/04/05/mol.115.101386.abstract
AB Malaria is a critical public health issue in the tropical world causing extensive morbidity and mortality. Infection by unicellular, obligate intracellular Plasmodium parasites causes malaria. The emergence of resistance to current antimalarial drugs necessitates the development of novel therapeutics. A potential novel drug target is the purine import transporter. Because Plasmodium parasites are purine auxotrophic, to fulfill metabolic requirements they must import purines from their host. They import purines via Equilibrative Nucleoside Transporter 1 (ENT1) homologues. Recently, we used a yeast-based high throughput screen (HTS) to identify inhibitors of the Plasmodium falciparum ENT1 (PfENT1) that kill P. falciparum parasites in culture. P. berghei infection of mice is an animal model for human malaria. Because P. berghei ENT1 (PbENT1) shares only 60% amino acid sequence identity with PfENT1, we sought to characterize PbENT1 and its sensitivity to our PfENT1 inhibitors. We expressed PbENT1 in purine auxotrophic yeast and used radiolabeled substrate uptake to characterize its function. We showed that PbENT1 transports both purines and pyrimidines. It preferred nucleosides compared to nucleobases. Inosine (IC50=3.7 μM) and guanosine (IC50=21.3 μM) had the highest affinities. Our recently discovered PfENT1 inhibitors were equally effective against both PbENT1 and PfENT1 mediated purine uptake. The PfENT1 inhibitors are at least 10-fold more potent against PfENT1 than human hENT1. They kill P. berghei parasites in 24 hour ex vivo culture. Thus, the P. berghei murine malaria model may be useful to evaluate the efficacy of PfENT1 inhibitors in vivo and their therapeutic potential for treatment of malaria.