title: Glutathione transport: a new role for PfCRT in chloroquine resistance.
abstract: OBJECTIVE
  Chloroquine (CQ) kills Plasmodium falciparum by binding heme, preventing its detoxification to hemozoin in the digestive vacuole (DV) of the parasite. CQ resistance (CQR) is associated with mutations in the DV membrane protein P. falciparum chloroquine resistance transporter (PfCRT), mediating the leakage of CQ from the DV. However, additional factors are thought to contribute to the resistance phenotype. This study tested the hypothesis that there is a link between glutathione (GSH) and CQR.
  
  
  RESULTS
  Using isogenic parasite lines carrying wild-type or mutant pfcrt, we reveal lower levels of GSH in the mutant lines and enhanced sensitivity to the GSH synthesis inhibitor l-buthionine sulfoximine, without any alteration in cytosolic de novo GSH synthesis. Incubation with N-acetylcysteine resulted in increased GSH levels in all parasites, but only reduced susceptibility to CQ in PfCRT mutant-expressing lines. In support of a heme destruction mechanism involving GSH in CQR parasites, we also found lower hemozoin levels and reduced CQ binding in the CQR PfCRT-mutant lines. We further demonstrate via expression in Xenopus laevis oocytes that the mutant alleles of Pfcrt in CQR parasites selectively transport GSH.
  
  
  METHODS
  We propose a mechanism whereby mutant pfcrt allows enhanced transport of GSH into the parasite's DV. The elevated levels of GSH in the DV reduce the level of free heme available for CQ binding, which mediates the lower susceptibility to CQ in the PfCRT mutant parasites.
  
  
  CONCLUSIONS
  PfCRT has a dual role in CQR, facilitating both efflux of harmful CQ from the DV and influx of beneficial GSH into the DV.
authors.affiliation: Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Patzewitz
authors.forename: J Enrique
authors.initials: JE
authors.lastname: Salcedo-Sora
authors.forename: Eleanor H
authors.initials: EH
authors.lastname: Wong
authors.forename: Sonal
authors.initials: S
authors.lastname: Sethia
authors.forename: Paul A
authors.initials: PA
authors.lastname: Stocks
authors.forename: Spencer C
authors.initials: SC
authors.lastname: Maughan
authors.forename: James A H
authors.initials: JA
authors.lastname: Murray
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Krishna
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Bray
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Ward
authors.forename: Sylke
authors.initials: S
authors.lastname: Müller
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D000962:Antimalarials / Q000378:metabolism / Q000494:pharmacology*; D001692:Biological Transport; D002478:Cells, Cultured; D002738:Chloroquine / Q000378:metabolism / Q000494:pharmacology*; D004351:Drug Resistance; D004912:Erythrocytes / Q000378:metabolism / Q000469:parasitology; D016166:Free Radical Scavengers / Q000494:pharmacology; D015870:Gene Expression; D005978:Glutathione / Q000378:metabolism*; D005981:Glutathione Synthase / Q000235:genetics / Q000378:metabolism; D006420:Hemeproteins / Q000378:metabolism; D006801:Humans; D026901:Membrane Transport Proteins / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000187:drug effects / Q000378:metabolism*; D021381:Protein Transport; D015800:Protozoan Proteins / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D000962:Antimalarials; D016166:Free Radical Scavengers; D006420:Hemeproteins; D026901:Membrane Transport Proteins; C416369:PfCRT protein, Plasmodium falciparum; D015800:Protozoan Proteins; C020753:hemozoin; D002738:Chloroquine; D005981:Glutathione Synthase; D005978:Glutathione; D000111:Acetylcysteine