RESUMO
Chloroquine (CQ) resistance (CQR) in Plasmodium falciparum malaria is widespread and has limited the use of CQ in many regions of the globe. Malaria caused by the related human parasite P. vivax is as widespread as is P. falciparum malaria and has been treated with CQ as extensively as has P. falciparum, suggesting that P. vivax parasites have been selected with CQ as profoundly as have P. falciparum parasites. Indeed, a growing number of clinical reports have presented data suggesting increased P. vivax CQR. Cytostatic (growth inhibitory) CQR for P. falciparum is caused by Plasmodium falciparum chloroquine resistance transporter (PfCRT) mutations, and it has been proposed that mutations in the PvCRT orthologue may simliarly cause P. vivax CQR via increasing CQ transport from the P. vivax digestive vacuole. Here we report the first quantitative analysis of drug transport mediated by all known mutant isoforms of Plasmodium vivax chloroquine resistance transporter (PvCRT) in order to test the protein's potential link to growing P. vivax CQR phenomena. Small, but statistically significant, differences in the transport of CQ and other quinoline antimalarial drugs were found for multiple PvCRT isoforms, relative to wild type PvCRT, suggesting that mutations in PvCRT can contribute to P. vivax CQR and other examples of quinoline antimalarial drug resistance.
Assuntos
Antimaláricos/metabolismo , Cloroquina/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Modelos Moleculares , Mutação , Plasmodium vivax/metabolismo , Proteínas de Protozoários/metabolismo , Substituição de Aminoácidos , Antimaláricos/farmacologia , Transporte Biológico , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Cloroquina/farmacologia , Contagem de Colônia Microbiana , Resistência a Medicamentos , Humanos , Malária Vivax/tratamento farmacológico , Malária Vivax/parasitologia , Proteínas de Membrana Transportadoras/química , Proteínas de Membrana Transportadoras/genética , Mutagênese Sítio-Dirigida , Plasmodium vivax/efeitos dos fármacos , Plasmodium vivax/crescimento & desenvolvimento , Plasmodium vivax/isolamento & purificação , Primaquina/metabolismo , Primaquina/farmacologia , Conformação Proteica , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteínas de Protozoários/química , Proteínas de Protozoários/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/crescimento & desenvolvimento , Saccharomyces cerevisiae/metabolismo , TrítioRESUMO
The Plasmodium falciparum malarial parasite genome appears to encode one and only one phosphatidylinositol 3'-kinase (PI3K), and sequence analysis suggests that the enzyme is a "class III"- or "Vps34"-type PI3K. PfVps34 has generated excitement as a possible druggable target and potentially a key target of artemisinin-based antimalarials. In this study, we optimize the PfVps34 gene for heterologous expression in yeast, purify the protein to homogeneity, use a recently validated quantitative assay for phosphatidylinositol 3'-phosphate production from phosphatidylinositol ( Hassett et al., companion paper; DOI 10.1021/acs.biochem.7b00416 ) to quantify activity and drug inhibition of that activity, and investigate the importance of key residues in the enzyme's catalytic and "N-lobe" domains. Data suggest that PfVps34 is indeed inhibited by artemisinin and related drugs but only under conditions that cleave the drugs' endoperoxide bridge to generate reactive alkylating agents.
