Affinage · Plasmodium

CRT

PF3D7_0709000 · chloroquine resistance transporter

Annotated
2026-09-08
98 papers in source corpus 28 papers cited in narrative 28 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CRT (PF3D7_0709000) is an integral digestive vacuole (DV) membrane transporter of Plasmodium falciparum whose native function is the H+-coupled export of short hemoglobin-derived peptides (4–11 residues) from the acidic DV lumen to the parasite cytosol, supplying amino acids for metabolism and relieving osmotic stress (PMID:32764664, PMID:25733858). It resides constitutively in the DV membrane throughout the intra-erythrocytic cycle (PMID:11090624, PMID:18769730). Point mutations in CRT are the central determinant of verapamil-reversible chloroquine resistance, established through genetic mapping and allelic-exchange transfection across parasite lines of diverse geographic origin (PMID:11090624, PMID:15813727). These mutations, most critically K76T, reconfigure a central electronegative substrate cavity resolved by cryo-EM at 3.2 Å, converting CRT into an active efflux pump that removes chloroquine—together with H+—from the DV down its electrochemical gradient, thereby lowering drug accumulation at its site of heme detoxification (PMID:31776516, PMID:18852275, PMID:19779197). The transporter is polyspecific: mutant isoforms also efflux quinine, lumefantrine, mefloquine, and piperaquine, with drug repertoire and resistance level tuned by specific accessory mutations (e.g. C350R, F145I, C101F) and by parasite genetic background (PMID:42410209, PMID:35507548, PMID:28487425, PMID:26261345, PMID:20485514). Acquisition of drug-transport capacity comes at the expense of peptide transport, and this functional trade-off—mechanistically traced to K76T disrupting peptide binding in the same cavity used for drug efflux—produces hemoglobin-peptide accumulation and a fitness cost that drives re-emergence of susceptible parasites when drug pressure is relaxed (PMID:24391526, PMID:40140375, PMID:32764664). Mutant CRT additionally imports glutathione into the DV, reducing free heme available for chloroquine binding (PMID:23256874), and its chloroquine-transport activity is modulated by redox-dependent disulfide bonds in loop 7 (PMID:41810826).

Mechanistic history

Synthesis pass · year-by-year structured walk · 16 steps
  1. 2000 High

    Established CRT as the genetic locus of chloroquine resistance and placed it at the digestive vacuole membrane, converting a mapped phenotype into a candidate transport protein.

    Evidence Genetic mapping of a chromosome 7 segment, transfection, subcellular localization and DV pH measurement in P. falciparum

    PMID:11090624

    Open questions at the time
    • Did not demonstrate direct drug transport
    • Native physiological substrate unknown
    • Mechanism of altered flux vs. altered pH not disentangled
  2. 2003 High

    Showed that resistance is dose-dependent on CRT expression, demonstrating that the amount of transporter, not just its sequence, sets the resistance level.

    Evidence 3'-UTR truncation allelic exchange lowering CRT expression, drug IC50 and single-cell DV pH assays in P. falciparum 7G8

    PMID:12813054

    Open questions at the time
    • Molecular transport mechanism still inferred from pH, not measured directly
    • Did not identify transported species
  3. 2005 High

    Transfection provided causal genetic proof that pfcrt mutations confer verapamil-reversible chloroquine resistance and extended CRT's role to quinine, consolidating it as an efflux transporter.

    Evidence Allelic exchange and verapamil-modulated drug susceptibility assays in P. falciparum

    PMID:15813727

    Open questions at the time
    • Direct transport not yet reconstituted
    • Structural basis of substrate selectivity unresolved
  4. 2006 Medium

    Mapped resistance-determining and selectivity residues to transmembrane segments 1, 4, and 9, defining the substrate recognition/translocation domain of CRT.

    Evidence Single-step drug selection generating isogenic TM1/TM9 mutants with drug accumulation and stereospecificity assays in P. falciparum 106/1

    PMID:17163969

    Open questions at the time
    • Residue roles inferred from selection, not structure
    • No transport reconstitution of individual mutants
  5. 2008 High

    Demonstrated a chloroquine-associated H+ leak from the DV in isogenic mutant lines, indicating drug and proton are co-transported by mutant CRT.

    Evidence Isogenic pfcrt transfectants and fluorometric DV H+ leak measurements in P. falciparum; CRT localized to DV membrane across the cycle by IFA/immuno-EM

    PMID:18769730 PMID:18852275

    Open questions at the time
    • Stoichiometry of H+/drug coupling not defined
    • Direct drug flux still not measured in isolation
  6. 2009 High

    Reconstitution in Xenopus oocytes proved that mutant, but not wild-type, CRT directly transports chloroquine, resolving whether resistance is transport-mediated.

    Evidence Xenopus oocyte expression with radiolabeled CQ transport and verapamil/CQ-analog inhibition in P. falciparum; isogenic lines linking K76T to lumefantrine susceptibility

    PMID:19210165 PMID:19779197

    Open questions at the time
    • Native physiological substrate still unknown
    • Whether drug transport is gain or repurposing of a native activity unresolved
  7. 2012 Medium

    Revealed a second resistance activity—glutathione import into the DV by mutant CRT—linking CRT to heme availability and chloroquine binding.

    Evidence Xenopus oocyte GSH transport, isogenic parasite GSH/heme fractionation and BSO sensitivity assays in P. falciparum

    PMID:23256874

    Open questions at the time
    • Relative contribution of GSH import vs. CQ efflux to resistance not quantified
    • Single lab
  8. 2014 High

    Systematic variant analysis and QTL mapping defined the mutational logic of resistance and its fitness cost, showing convergent, order-constrained acquisition of CQ transport at the expense of peptide handling.

    Evidence >100 CRT variants in Xenopus oocytes with kinetic analysis; mQTL mapping of hemoglobin-peptide accumulation and growth competition in P. falciparum

    PMID:24391526 PMID:24728833

    Open questions at the time
    • Native substrate identity still inferred from peptide accumulation
    • Structural basis of the transport/fitness trade-off unresolved
  9. 2015 High

    Proteoliposome reconstitution defined CRT as a H+-coupled polyspecific exporter of nutrients and drugs, and accessory mutations (C350R, C101F/L272F) were shown to reshape drug transport and resistance profiles.

    Evidence Purified CRT proteoliposome uptake of multiple substrates; genome/gene editing of C350R, C101F, L272F and diverse haplotypes with drug/fitness assays in P. falciparum (incl. 7G8)

    PMID:25733858 PMID:25898991 PMID:26261345 PMID:26420308

    Open questions at the time
    • Physiological relevance of all in vitro substrates unclear
    • How accessory mutations remodel the cavity not structurally defined
  10. 2016 High

    Combinatorial editing of full haplotypes showed K76T alone is insufficient for full resistance and that mutations arrive in constrained order, mapping the adaptive landscape of CRT evolution.

    Evidence Zinc-finger nuclease editing of all intermediate Ecu1110/7G8 alleles with drug and growth phenotyping and evolutionary modeling in P. falciparum

    PMID:26908582

    Open questions at the time
    • Structural effect of each intermediate not resolved
    • In vivo selection dynamics inferred from in vitro fitness
  11. 2017 High

    Linked CRT-mediated drug transport to shared inhibition of DV heme detoxification and extended the transporter's reach to piperaquine, with C101F reprogramming the drug-resistance spectrum.

    Evidence ZFN editing of C101F into Dd2 CRT with IC90/LD50, heme fractionation and hemoglobin proteolysis assays in P. falciparum Dd2

    PMID:28487425

    Open questions at the time
    • Single mutation studied in one background
    • Structural mechanism of PPQ gain-of-transport not resolved here
  12. 2019 High

    The cryo-EM structure provided the atomic framework: a central negatively charged cavity where resistance mutations line the drug-binding site, explaining polyspecific, membrane-potential- and pH-dependent efflux and PPQ-transport gain via F145I/C350R.

    Evidence 3.2 Å single-particle cryo-EM of 7G8 CRT with Fab, binding/transport assays and gene-edited F145I/C350R validation in P. falciparum 7G8

    PMID:31776516

    Open questions at the time
    • Only one isoform structure solved
    • Conformational cycle of transport not captured
    • Wild-type native-substrate-bound structure absent
  13. 2020 High

    Identified the physiological substrate—short hemoglobin-derived peptides (4–11 residues)—establishing CRT's native role in nutrient export and osmotic homeostasis, and showing resistance mutations degrade this function.

    Evidence Xenopus oocyte and in situ transport assays with diverse substrates plus parasite metabolomics comparing wild-type and mutant isoforms in P. falciparum

    PMID:32764664

    Open questions at the time
    • Downstream metabolic fate of exported peptides not mapped
    • Whether peptide export is the sole essential function unclear
  14. 2022 High

    Showed mutant CRT effluxes lumefantrine and mefloquine as well as chloroquine, providing a transport-redistribution basis for collateral drug sensitivity in resistant parasites.

    Evidence Xenopus oocyte and live-parasite drug distribution assays across multiple CRT isoforms in P. falciparum

    PMID:35507548

    Open questions at the time
    • Quantitative contribution to clinical partner-drug outcomes not established
    • Single lab
  15. 2025 Medium

    Molecular dynamics resolved the functional conflict at the residue level: K76T opens the cavity to chloroquine while disrupting peptide binding, explaining the transport/fitness trade-off.

    Evidence 130 µs MD simulations of sensitive and resistant isoforms with CQ and peptide substrates

    PMID:40140375

    Open questions at the time
    • Computational only, no direct experimental validation in this study
    • Full transport cycle not simulated
  16. 2026 High

    Established redox regulation of CRT transport (L7 disulfide bonds and modulatory cysteines) and consolidated CRT as the direct mediator of quinine partial resistance and a druggable efflux target whose inhibition reverses resistance.

    Evidence Cysteine mutagenesis/redox-controlled ISOV transport and MD in Dd2; genetic cross QTL plus proteoliposome quinine transport; drug-pressure selection plus proteoliposome assays and metabolomics with ZY19489 in P. falciparum

    PMID:41810826 PMID:41922323 PMID:42410209

    Open questions at the time
    • Physiological redox trigger in the DV not defined
    • Clinical translatability of CRT-transport inhibitors untested
    • How inhibitor-selected mutations remodel the cavity not structurally resolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • It remains unresolved how CRT alternates between its native peptide-export and mutant drug-efflux modes at the level of a full conformational transport cycle, and whether pharmacological blockade of CRT-mediated efflux can be exploited therapeutically in vivo.
  • No structure of a native-substrate-bound or transport-intermediate state
  • In vivo efficacy of CRT-efflux inhibitors unestablished
  • Interplay of redox regulation, expression level, and genetic background not integrated into one quantitative model

Mechanism profile

Synthesis pass · controlled-vocabulary classification
No controlled-vocabulary terms were assigned to this entry.

Evidence

Reading pass · 28 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2000 CRT (PfCRT) localizes to the parasite digestive vacuole (DV) membrane; point mutations in CRT associate completely with verapamil-reversible chloroquine resistance across parasite lines from Asia, Africa, and South America, and increased DV acidification associates with CRT point mutations, implicating CRT in altered chloroquine flux or reduced drug binding to hematin through effects on DV pH. Genetic mapping of a 36 kb chromosome 7 segment, transfection studies, single-step drug selection generating a novel K76I mutation, subcellular localization to the digestive vacuole, pH measurements Molecular cell High 11090624
2004 Bioinformatic analysis places CRT within the drug/metabolite transporter (DMT) superfamily; the protein is predicted to function as a dimer with termini in the parasite cytosol; the key CQ-resistance-conferring K76T mutation localizes to a region implicated in substrate selectivity and is predicted to allow transport of the cationic (protonated) form of chloroquine down its concentration gradient out of the acidic vacuole. Detailed bioinformatic/phylogenetic analysis of transmembrane topology, sequence comparison with DMT superfamily members Molecular biology and evolution Low 15240840
2003 Reduction of CRT expression levels by ~30–40% (via 3′-UTR truncation allelic exchange) in chloroquine-resistant 7G8 parasites causes up to 40% decrease in chloroquine IC50 and alters intracellular pH of the digestive vacuole, demonstrating that CRT expression level directly modulates the degree of chloroquine resistance. Allelic exchange to truncate pfcrt 3′-UTR; transient transfection reporter assays; [3H]hypoxanthine incorporation drug assays; single-cell photometric pH analysis The Journal of biological chemistry High 12813054
2004 Purified CRT protein specifically binds chloroquine (KD ~400 nM) but does not measurably bind quinine at physiologically relevant concentrations; inside-out plasma membrane vesicles from strains harboring mutant CRT show lower passive accumulation of CQ than expected despite higher ΔpH, consistent with active CQ export by mutant CRT. Overexpression in Pichia pastoris; purified membrane/inside-out vesicle (ISOV) binding and transport studies Biochemistry Medium 15222741
2005 Transfection studies directly proved that pfcrt mutations confer verapamil-reversible chloroquine resistance in vitro and revealed an important role for CRT mutations in quinine resistance; available evidence is consistent with CRT functioning as a transporter that directly mediates efflux of chloroquine from the digestive vacuole. Transfection/allelic exchange in P. falciparum; drug susceptibility assays with and without verapamil Molecular microbiology High 15813727
2006 Single-step drug selection of isogenic parasites identified novel CRT mutations in transmembrane domains 1 (C72R, K76N, K76I, K76T) and 9 (Q352K, Q352R); charge-altering mutations in TM1 and TM9, combined with a previously described S163R mutation in TM4, demonstrate that TM segments 1, 4, and 9 provide important structural components of a substrate recognition and translocation domain controlling drug accumulation in the DV and stereospecific quinoline responses. Single-step drug selection; isogenic clone generation; quantitative CQ susceptibility assays; DV drug accumulation measurements; quinine/quinidine stereospecificity assays Molecular microbiology Medium 17163969
2008 Using transfectant parasite strains of identical genetic background differing only in their pfcrt allele, CRT resistance-conferring mutations are shown to cause a chloroquine-associated H+ leak from the digestive vacuole, consistent with mutant CRT mediating efflux of chloroquine together with H+ from the DV. Isogenic transfectant parasites (same background, different pfcrt alleles); fluorometric DV pH/H+ leak measurements in the presence and absence of chloroquine Antimicrobial agents and chemotherapy High 18852275
2009 Mutant (CQ-resistant) CRT expressed at the surface of Xenopus laevis oocytes transports chloroquine, whereas the wild-type CRT does not; CQ transport via mutant CRT is inhibited by CQ analogs and by the resistance-reverser verapamil, establishing that CQ resistance is due to direct transport of the drug via mutant CRT. Xenopus laevis oocyte expression system; radiolabeled CQ transport assays; pharmacological inhibition with CQ analogs and verapamil Science High 19779197
2009 The CRT K76T mutation in parasites directly reduces lumefantrine susceptibility; isogenic pfcrt-modified parasite lines demonstrated a 2-fold increase in lumefantrine susceptibility attributable to the K76T mutation, and AL treatment in vivo selects for the CQ-susceptible pfcrt K76 allele. Isogenic pfcrt-modified parasite lines (zinc-finger nuclease or allelic exchange); in vitro drug susceptibility assays; in vivo clinical trial with molecular genotyping before and after treatment The Journal of infectious diseases High 19210165
2010 Mutant CRT alleles from the 7G8 haplotype, when introduced into multiple CQ-sensitive strain backgrounds by allelic exchange, confer strain-dependent CQ responses ranging from high-level resistance to a CQ-tolerance phenotype that does not meet resistance criteria; this demonstrates that CQ resistance level is dependent on both the pfcrt allele and the parasite genetic background. Variant pfcrt alleles also modulate susceptibility to other ACT partner drugs in a strain-dependent manner. Allelic exchange replacing wild-type pfcrt with 7G8 mutant allele in three CQ-sensitive strain backgrounds; in vitro drug susceptibility assays PLoS pathogens High 20485514
2012 Mutant CRT alleles in CQ-resistant parasites transport glutathione (GSH) into the digestive vacuole (demonstrated by Xenopus oocyte expression); elevated DV GSH reduces free heme available for CQ binding, lowering hemozoin levels and CQ binding in mutant CRT lines; CQR parasites also show lower cytosolic GSH and enhanced sensitivity to the GSH synthesis inhibitor BSO. CRT thus has a dual role in CQR: efflux of CQ from the DV and import of GSH into the DV. Xenopus laevis oocyte GSH transport assays; isogenic parasite lines with wild-type or mutant pfcrt; GSH level measurements; heme fractionation; CQ binding assays; BSO sensitivity assays Antioxidants & redox signaling Medium 23256874
2014 In a genetic cross between CQ-susceptible and CQ-resistant parasites, accumulation of hemoglobin-derived peptides maps via mQTL to CQR alleles of pfcrt; CRT mutations impair hemoglobin digestion, causing peptide accumulation, drug resistance, and reduced fitness — providing a molecular explanation for the fitness cost of CQR parasites and the re-emergence of CQ-susceptible parasites when drug pressure is removed. Metabolic quantitative trait locus (mQTL) mapping in genetic cross progeny; metabolomics (hemoglobin-derived peptide measurement); in vitro growth competition assays PLoS genetics High 24391526
2014 More than 100 PfCRT variants expressed in Xenopus oocytes show that multiple distinct mutational pathways all converge on saturable CQ transport activity; a minimum of 2 mutations suffice for low CQ transport and as few as 4 confer full activity; mutations must be added in a specific order to avoid reductions in activity; the saturable nature of transport suggests resistance could be overcome by reoptimizing CQ dosage. Xenopus laevis oocyte expression of >100 CRT variants; radiolabeled CQ transport assays; kinetic characterization Proceedings of the National Academy of Sciences of the United States of America High 24728833
2015 CRT mutations (C101F or L272F), selected by amantadine or blasticidin pressure, cause development of enlarged food vacuoles and increased sensitivity to CQ; introduction of C101F or L272F into a CQ-resistant CRT variant reduces its ability to transport CQ by ~93% and ~82% respectively in Xenopus oocytes, providing a mechanistic explanation for the increased CQ sensitivity. Drug-pressure selection; transgenic parasite lines expressing L272F CRT; Xenopus oocyte CQ transport assays; microscopic food vacuole size measurement; drug IC50 assays Scientific reports High 26420308
2015 CRT is a H+-coupled polyspecific nutrient and drug exporter: reconstituted in proteoliposomes, CQ-resistant and CQ-sensitive CRT isoforms actively take up tetraethylammonium, verapamil, CQ, basic amino acids, polypeptides, and polyamines at the expense of an electrochemical proton gradient; CQ-resistant CRT exhibits decreased affinity for CQ resulting in increased net CQ uptake; CQ competitively inhibits amino acid transport. Proteoliposome reconstitution with purified CRT isoforms; electrochemical proton-gradient-driven uptake assays for multiple substrates; competitive inhibition experiments Proceedings of the National Academy of Sciences of the United States of America High 25733858
2015 Acquisition of the C350R mutation in the CQ-resistant 7G8 pfcrt allele (identified by GWAS in French Guiana) causes complete loss of CQ resistance when introduced by genome editing; C350R is associated with decreased piperaquine susceptibility in vitro, suggesting PPQ pressure selected for this mutation after CQ withdrawal. Genome-wide association study in field isolates; genome editing (allelic exchange) of the CQR 7G8 strain to incorporate C350R; in vitro drug susceptibility assays; retrospective molecular survey Proceedings of the National Academy of Sciences of the United States of America High 26261345
2016 Combinatorial genetic modification of the pfcrt locus using zinc-finger nucleases to produce all possible combinations of intermediate alleles in the Ecuadorian Ecu1110 haplotype (K76T/A220S/N326D/I356L) and related 7G8 haplotype revealed: K76T alone is insufficient for full CQR; additional mutations contribute to resistance and fitness; monodesethyl-CQ and amodiaquine may have driven mutant pfcrt evolution; parasites navigated constrained adaptive landscapes via probabilistically rare mutational bursts. Zinc-finger nuclease gene editing to create all combinatorial pfcrt allele intermediates; in vitro drug susceptibility assays; in vitro growth profiling; evolutionary modeling Molecular biology and evolution High 26908582
2017 Addition of the C101F mutation to the CQ-resistant Dd2 CRT isoform via zinc-finger nuclease gene editing confers piperaquine (PPQ) resistance in cultured parasites (higher IC90 and LD50 for PPQ), reverses Dd2-mediated CQ resistance, and sensitizes parasites to amodiaquine, quinine, and artemisinin while conferring amantadine and blasticidin resistance; heme fractionation assays show PPQ causes buildup of reactive free heme and inhibits hemozoin formation, indicating inhibition of heme detoxification in the DV as a primary mode of action shared with CQ. Zinc-finger nuclease gene editing (C101F into Dd2 CRT); IC90 and LD50 drug assays; heme fractionation assays; hemoglobin proteolysis assays mBio High 28487425
2019 The cryo-EM structure of CRT (7G8 isoform, PPQ-sensitive, CQ-resistant) was solved at 3.2 Å resolution using single-particle cryo-EM with antigen-binding fragment technology; mutations conferring CQ and PPQ resistance localize primarily to moderately conserved sites on distinct helices lining a central negatively charged cavity — the principal site of interaction with positively charged drugs; binding and transport studies show 7G8 CRT binds CQ and PPQ with comparable affinities and they are mutually competitive; 7G8 CRT transports CQ in a membrane potential- and pH-dependent manner (active efflux) but does not transport PPQ; newly emerging F145I and C350R mutations can mediate PPQ transport in 7G8 variant proteins and confer resistance in gene-edited parasites. Single-particle cryo-EM (3.2 Å); antigen-binding fragment technology; drug binding assays; Xenopus oocyte transport assays; gene editing of F145I and C350R variants; in silico analyses Nature High 31776516
2020 CRT transports host-derived peptides of 4–11 residues (varying in charge and composition) as its natural substrates in vitro and in situ; CRT does not mediate non-specific transport of other metabolites or ions; drug-resistance-conferring mutations reduce both the peptide transport capacity and substrate range of CRT; CRT transports peptides from the digestive vacuole lumen to the cytosol, providing amino acids for parasite metabolism and preventing osmotic stress of the DV. Xenopus oocyte expression assays with diverse candidate substrates; metabolomics in parasites; in situ peptide transport assays; comparison of wild-type vs. resistant isoforms Nature communications High 32764664
2022 Mutant CRT isoforms (CQ-resistant) transport chloroquine, lumefantrine, and mefloquine out of the digestive vacuole, whereas wild-type CRT does not transport these drugs; this redistribution keeps drugs in the cytosol, away from DV targets, explaining collateral drug sensitivity to lumefantrine and mefloquine in CQ-resistant parasites. The mechanistic model established uses Xenopus oocyte assays and live parasite assays. Xenopus oocyte expression system for CRT transport assays; live parasite drug distribution assays; comparison of multiple CRT isoforms PLoS biology High 35507548
2025 Molecular dynamics simulations (130 μs total) of CQ-sensitive and CQ-resistant CRT isoforms identify the CQ binding site within the central cavity; the K76T mutation allows CQ to access the binding site but disrupts peptide binding by altering cavity charge, providing molecular-level explanation for the functional conflict between CQ transport and peptide transport in mutant CRT. Molecular dynamics simulations (130 μs) of CQ-sensitive and CQ-resistant isoforms with CQ and peptide substrates; structural analysis of binding modes Nature communications Medium 40140375
2026 CQ transport by CRT is regulated by the redox potential of the digestive vacuole environment; disulfide bonds form at C289/C312 and C301/C309 pairs in loop 7 (L7) of the Dd2 CRT isoform and are required for full CQ transport activity; site-specific mutagenesis of all cysteines identifies C101, C139, C171, and C328 as additionally modulating CQ transport; MD simulations show large conformational changes in L7 upon SH-to-S-S interconversion near the initial drug binding site. Site-specific mutagenesis of all cysteines; maleimide labeling; redox buffering; CQ transport measurements (Pichia pastoris/ISOV system); molecular dynamics (MD) calculations Biochemistry Medium 41810826
2026 ZY19489-resistant parasites acquire a novel CRT mutation that blocks mutant CRT-mediated PPQ and chloroquine efflux from the DV; uptake studies in proteoliposomes loaded with drug-resistant CRT isoforms demonstrate that ZY19489 inhibits mutant CRT-mediated PPQ and CQ transport; this renders ZY19489-resistant parasites hypersusceptible to PPQ and reverses CQ resistance. Metabolomics shows ZY19489 reduces intracellular levels of short hemoglobin-derived peptides (natural CRT substrates) and increases pyrimidine deoxynucleotides. In vitro drug pressure selection; proteoliposome transport assays with drug-resistant CRT isoforms; parasite drug susceptibility assays; metabolomics Nature communications High 41922323
2026 In a P. falciparum genetic cross combined with QTL analysis and gene-editing studies, CRT (chromosome 7 candidate) is identified as a primary mediator of quinine partial resistance; in proteoliposome assays, mutant CRT isoforms transport more quinine than wild-type CRT, establishing CRT's direct role in quinine efflux. P. falciparum genetic cross using human liver-chimaeric mouse model; QTL analysis of 120 recombinant progeny; gene-editing studies; proteoliposome quinine transport assays Nature microbiology High 42410209
2008 CRT is present as a component of the digestive vacuole membrane throughout the intra-erythrocytic cycle; the vacuolar membrane contains both MSP1(19) (a marker for food vacuole biogenesis) and CRT, and CRT remains a constitutive component of the DV membrane from ring through trophozoite and schizont stages. Immunofluorescence imaging; immuno-electron microscopy; metabolic labeling; co-localization with MSP1(19) PloS one Medium 18769730
2005 Primaquine (8-aminoquinoline) blocks mutant CRT function, as demonstrated using matched transfectants expressing mutant versus wild-type pfcrt alleles; primaquine's synergy with CQ against CQ-resistant P. falciparum is directly attributable to its ability to block CRT, thereby enhancing CQ accumulation in the DV. Matched transfectant parasite lines (mutant vs. wild-type pfcrt); drug combination assays (CQ + primaquine); pharmacological characterization Biochemical pharmacology Medium 16139253
2015 Geographically diverse CRT haplotypes (Philippines PH1/PH2, Cambodia Cam734) engineered into isogenic P. falciparum by zinc-finger nuclease gene editing confer moderate CQ resistance, reduce growth rates (PH1/PH2), or enhance growth rates (Cam734) in competition assays; all three haplotypes mediate cross-resistance to amodiaquine and render parasites more susceptible to lumefantrine, revealing ongoing region-specific CRT evolution that simultaneously impacts drug susceptibility and fitness. Zinc-finger nuclease gene editing; in vitro drug susceptibility assays; co-culture competition growth assays Molecular microbiology High 25898991

Source papers

Stage 0 corpus · 98 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2000 Mutations in the P. falciparum digestive vacuole transmembrane protein PfCRT and evidence for their role in chloroquine resistance. Molecular cell 1200 11090624
2004 Mefloquine resistance in Plasmodium falciparum and increased pfmdr1 gene copy number. Lancet (London, England) 672 15288742
2015 Genetic architecture of artemisinin-resistant Plasmodium falciparum. Nature genetics 471 25599401
2019 Determinants of dihydroartemisinin-piperaquine treatment failure in Plasmodium falciparum malaria in Cambodia, Thailand, and Vietnam: a prospective clinical, pharmacological, and genetic study. The Lancet. Infectious diseases 293 31345710
2016 Globally prevalent PfMDR1 mutations modulate Plasmodium falciparum susceptibility to artemisinin-based combination therapies. Nature communications 251 27189525
2009 Chloroquine transport via the malaria parasite's chloroquine resistance transporter. Science (New York, N.Y.) 234 19779197
2014 Polymorphisms in Plasmodium falciparum chloroquine resistance transporter and multidrug resistance 1 genes: parasite risk factors that affect treatment outcomes for P. falciparum malaria after artemether-lumefantrine and artesunate-amodiaquine. The American journal of tropical medicine and hygiene 233 25048375
2019 Evolution and expansion of multidrug-resistant malaria in southeast Asia: a genomic epidemiology study. The Lancet. Infectious diseases 229 31345709
2020 Molecular Mechanisms of Drug Resistance in Plasmodium falciparum Malaria. Annual review of microbiology 221 32905757
2012 PfCRT and its role in antimalarial drug resistance. Trends in parasitology 217 23020971
2001 High-level chloroquine resistance in Sudanese isolates of Plasmodium falciparum is associated with mutations in the chloroquine resistance transporter gene pfcrt and the multidrug resistance Gene pfmdr1. The Journal of infectious diseases 208 11319692
2009 In vivo selection of Plasmodium falciparum parasites carrying the chloroquine-susceptible pfcrt K76 allele after treatment with artemether-lumefantrine in Africa. The Journal of infectious diseases 185 19210165
2021 Changing Prevalence of Potential Mediators of Aminoquinoline, Antifolate, and Artemisinin Resistance Across Uganda. The Journal of infectious diseases 167 33146722
2019 Structure and drug resistance of the Plasmodium falciparum transporter PfCRT. Nature 166 31776516
2004 The malaria parasite's chloroquine resistance transporter is a member of the drug/metabolite transporter superfamily. Molecular biology and evolution 154 15240840
2006 Transporters involved in resistance to antimalarial drugs. Trends in pharmacological sciences 144 16996622
2005 Defining the role of PfCRT in Plasmodium falciparum chloroquine resistance. Molecular microbiology 140 15813727
2009 In vitro activities of piperaquine, lumefantrine, and dihydroartemisinin in Kenyan Plasmodium falciparum isolates and polymorphisms in pfcrt and pfmdr1. Antimicrobial agents and chemotherapy 139 19770282
2023 Pf7: an open dataset of Plasmodium falciparum genome variation in 20,000 worldwide samples. Wellcome open research 131 36864926
2003 Recovery of chloroquine sensitivity and low prevalence of the Plasmodium falciparum chloroquine resistance transporter gene mutation K76T following the discontinuance of chloroquine use in Malawi. The American journal of tropical medicine and hygiene 122 12875289
2015 Adaptive evolution of malaria parasites in French Guiana: Reversal of chloroquine resistance by acquisition of a mutation in pfcrt. Proceedings of the National Academy of Sciences of the United States of America 120 26261345
2017 Association of a Novel Mutation in the Plasmodium falciparum Chloroquine Resistance Transporter With Decreased Piperaquine Sensitivity. The Journal of infectious diseases 99 28931241
2003 Chloroquine resistance modulated in vitro by expression levels of the Plasmodium falciparum chloroquine resistance transporter. The Journal of biological chemistry 98 12813054
2017 A Variant PfCRT Isoform Can Contribute to Plasmodium falciparum Resistance to the First-Line Partner Drug Piperaquine. mBio 96 28487425
2010 Exploring the contribution of candidate genes to artemisinin resistance in Plasmodium falciparum. Antimicrobial agents and chemotherapy 96 20421395
2010 Transporters as mediators of drug resistance in Plasmodium falciparum. International journal for parasitology 94 20399785
2005 Decreased prevalence of the Plasmodium falciparum chloroquine resistance transporter 76T marker associated with cessation of chloroquine use against P. falciparum malaria in Hainan, People's Republic of China. The American journal of tropical medicine and hygiene 90 15827277
2022 Plasmodium falciparum resistance to artemisinin-based combination therapies. Current opinion in microbiology 86 36007459
2006 Association between mutations in Plasmodium falciparum chloroquine resistance transporter and P. falciparum multidrug resistance 1 genes and in vivo amodiaquine resistance in P. falciparum malaria-infected children in Nigeria. The American journal of tropical medicine and hygiene 85 16837724
2003 Short report: association between chloroquine and amodiaquine resistance and allelic variation in the Plasmodium falciparum multiple drug resistance 1 gene and the chloroquine resistance transporter gene in isolates from the upper Nile in southern Sudan. The American journal of tropical medicine and hygiene 85 13677373
2010 Identification of a mutant PfCRT-mediated chloroquine tolerance phenotype in Plasmodium falciparum. PLoS pathogens 82 20485514
2001 Prevalence of the K76T mutation in the putative Plasmodium falciparum chloroquine resistance transporter (pfcrt) gene and its relation to chloroquine resistance in Mozambique. The Journal of infectious diseases 79 11294676
2011 Patterns of chloroquine use and resistance in sub-Saharan Africa: a systematic review of household survey and molecular data. Malaria journal 78 21554692
2004 Variations in the sequence and expression of the Plasmodium falciparum chloroquine resistance transporter (Pfcrt) and their relationship to chloroquine resistance in vitro. Molecular and biochemical parasitology 78 15478806
2005 pfcrt is more than the Plasmodium falciparum chloroquine resistance gene: a functional and evolutionary perspective. Acta tropica 76 15866507
2020 The natural function of the malaria parasite's chloroquine resistance transporter. Nature communications 75 32764664
2006 Mutations in transmembrane domains 1, 4 and 9 of the Plasmodium falciparum chloroquine resistance transporter alter susceptibility to chloroquine, quinine and quinidine. Molecular microbiology 75 17163969
2014 Metabolic QTL analysis links chloroquine resistance in Plasmodium falciparum to impaired hemoglobin catabolism. PLoS genetics 74 24391526
2008 Formation of the food vacuole in Plasmodium falciparum: a potential role for the 19 kDa fragment of merozoite surface protein 1 (MSP1(19)). PloS one 73 18769730
2004 Widespread occurrence of the Plasmodium falciparum chloroquine resistance transporter (Pfcrt) gene haplotype SVMNT in P. falciparum malaria in India. The American journal of tropical medicine and hygiene 73 15031513
2018 Next-Generation Sequencing and Bioinformatics Protocol for Malaria Drug Resistance Marker Surveillance. Antimicrobial agents and chemotherapy 72 29439965
2010 Amodiaquine resistance in Plasmodium falciparum malaria in Afghanistan is associated with the pfcrt SVMNT allele at codons 72 to 76. Antimicrobial agents and chemotherapy 70 20547800
2021 Drug susceptibility of Plasmodium falciparum in eastern Uganda: a longitudinal phenotypic and genotypic study. The Lancet. Microbe 69 34553183
2004 The antimalarial drug resistance protein Plasmodium falciparum chloroquine resistance transporter binds chloroquine. Biochemistry 68 15222741
2013 Discordance in drug resistance-associated mutation patterns in marker genes of Plasmodium falciparum and Plasmodium knowlesi during coinfections. The Journal of antimicrobial chemotherapy 64 23292346
2014 Diverse mutational pathways converge on saturable chloroquine transport via the malaria parasite's chloroquine resistance transporter. Proceedings of the National Academy of Sciences of the United States of America 63 24728833
2015 Mutations in the Plasmodium falciparum chloroquine resistance transporter, PfCRT, enlarge the parasite's food vacuole and alter drug sensitivities. Scientific reports 61 26420308
2009 Analysis of single-nucleotide polymorphisms in the crt-o and mdr1 genes of Plasmodium vivax among chloroquine-resistant isolates from the Brazilian Amazon region. Antimicrobial agents and chemotherapy 61 19451296
2015 Plasmodium falciparum chloroquine resistance transporter is a H+-coupled polyspecific nutrient and drug exporter. Proceedings of the National Academy of Sciences of the United States of America 59 25733858
2010 pfmdr1 amplification and fixation of pfcrt chloroquine resistance alleles in Plasmodium falciparum in Venezuela. Antimicrobial agents and chemotherapy 59 20145087
2014 Expression levels of pvcrt-o and pvmdr-1 are associated with chloroquine resistance and severe Plasmodium vivax malaria in patients of the Brazilian Amazon. PloS one 58 25157811
2016 The return of chloroquine-susceptible Plasmodium falciparum malaria in Zambia. Malaria journal 57 27919256
2005 Primaquine synergises the activity of chloroquine against chloroquine-resistant P. falciparum. Biochemical pharmacology 56 16139253
2003 Polymorphism in the Plasmodium falciparum chloroquine-resistance transporter protein links verapamil enhancement of chloroquine sensitivity with the clinical efficacy of amodiaquine. Malaria journal 56 14599295
2009 Plasmodium falciparum Na+/H+ exchanger 1 transporter is involved in reduced susceptibility to quinine. Antimicrobial agents and chemotherapy 53 19273668
2016 Combinatorial Genetic Modeling of pfcrt-Mediated Drug Resistance Evolution in Plasmodium falciparum. Molecular biology and evolution 51 26908582
2003 New haplotypes of the Plasmodium falciparum chloroquine resistance transporter (pfcrt) gene among chloroquine-resistant parasite isolates. The American journal of tropical medicine and hygiene 51 12875286
2003 Molecular markers for drug resistance in malaria: use in treatment, diagnosis and epidemiology. Current opinion in infectious diseases 51 14624105
2015 Balancing drug resistance and growth rates via compensatory mutations in the Plasmodium falciparum chloroquine resistance transporter. Molecular microbiology 48 25898991
2022 Mechanistic basis for multidrug resistance and collateral drug sensitivity conferred to the malaria parasite by polymorphisms in PfMDR1 and PfCRT. PLoS biology 47 35507548
2010 On the mechanism of chloroquine resistance in Plasmodium falciparum. PloS one 47 21124966
2010 PfCRT-mediated drug transport in malarial parasites. Biochemistry 47 21142008
2006 Assessment of Plasmodium falciparum resistance to ferroquine (SSR97193) in field isolates and in W2 strain under pressure. Malaria journal 47 16464254
2005 A simple, high-throughput method to detect Plasmodium falciparum single nucleotide polymorphisms in the dihydrofolate reductase, dihydropteroate synthase, and P. falciparum chloroquine resistance transporter genes using polymerase chain reaction- and enzyme-linked immunosorbent assay-based technology. The American journal of tropical medicine and hygiene 47 15741552
2022 Prevalence of Plasmodium falciparum haplotypes associated with resistance to sulfadoxine-pyrimethamine and amodiaquine before and after upscaling of seasonal malaria chemoprevention in seven African countries: a genomic surveillance study. The Lancet. Infectious diseases 46 36328000
2012 Glutathione transport: a new role for PfCRT in chloroquine resistance. Antioxidants & redox signaling 46 23256874
2007 Short report: polymorphisms in the pfcrt and pfmdr1 genes of Plasmodium falciparum and in vitro susceptibility to amodiaquine and desethylamodiaquine. The American journal of tropical medicine and hygiene 46 18165517
2011 Quinoline antimalarials containing a dibemethin group are active against chloroquinone-resistant Plasmodium falciparum and inhibit chloroquine transport via the P. falciparum chloroquine-resistance transporter (PfCRT). Journal of medicinal chemistry 45 21875063
2016 Artesunate-Amodiaquine and Artemether-Lumefantrine Therapies and Selection of Pfcrt and Pfmdr1 Alleles in Nanoro, Burkina Faso. PloS one 44 27031231
2014 Selection of drug resistance-mediating Plasmodium falciparum genetic polymorphisms by seasonal malaria chemoprevention in Burkina Faso. Antimicrobial agents and chemotherapy 44 24733476
2013 Rapid selection of Plasmodium falciparum chloroquine resistance transporter gene and multidrug resistance gene-1 haplotypes associated with past chloroquine and present artemether-lumefantrine use in Inhambane District, southern Mozambique. The American journal of tropical medicine and hygiene 44 23382159
2013 Changes in malaria parasite drug resistance in an endemic population over a 25-year period with resulting genomic evidence of selection. The Journal of infectious diseases 44 24265439
2008 Chloroquine resistance-conferring mutations in pfcrt give rise to a chloroquine-associated H+ leak from the malaria parasite's digestive vacuole. Antimicrobial agents and chemotherapy 42 18852275
2014 Role of Different Pfcrt and Pfmdr-1 Mutations in Conferring Resistance to Antimalaria Drugs in Plasmodium falciparum. Malaria research and treatment 41 25506039
2004 Chloroquine resistance in Plasmodium chabaudi: are chloroquine-resistance transporter (crt) and multi-drug resistance (mdr1) orthologues involved? Molecular and biochemical parasitology 41 14668009
2017 Prevalence of mutations linked to antimalarial resistance in Plasmodium falciparum from Chhattisgarh, Central India: A malaria elimination point of view. Scientific reports 40 29192183
2004 Evidence for activation of endogenous transporters in Xenopus laevis oocytes expressing the Plasmodium falciparum chloroquine resistance transporter, PfCRT. The Journal of biological chemistry 40 15258157
2024 Prevalence of mutations associated with artemisinin partial resistance and sulfadoxine-pyrimethamine resistance in 13 regions in Tanzania in 2021: a cross-sectional survey. The Lancet. Microbe 39 39159629
2025 Rising prevalence of Plasmodium falciparum Artemisinin partial resistance mutations in Ethiopia. Communications medicine 17 40681807
2025 Pf8: an open dataset of Plasmodium falciparum genome variation in 33,325 worldwide samples. Wellcome open research 13 41267740
2025 Plasmodiumfalciparum protein kinase 6 and hemozoin formation are inhibited by a type II human kinase inhibitor exhibiting antimalarial activity. Cell chemical biology 10 40628257
2025 Prevalence of Plasmodium falciparum Drug Resistance Markers pfcrt K76T and pfaat1 S258L in Southern Rwanda, 2010 to 2023. The Journal of infectious diseases 4 39936828
2025 A CRISPR homing screen finds a chloroquine resistance transporter-like protein of the Plasmodium oocyst essential for mosquito transmission of malaria. Nature communications 4 40274854
2026 Geographical Heterogeneity in Antimalarial Resistance Markers by Genomic Surveillance in Angola, 2023. The American journal of tropical medicine and hygiene 3 41843937
2025 The plasmepsin-piperaquine paradox persists in Plasmodium falciparum. PLoS pathogens 3 40720544
2025 Indole-2-carboxamides Optimization for Antiplasmodial Activity. ACS bio & med chem Au 3 41112202
2026 Chloroquine resistance transporter drives divergent multi-locus drug resistance genetic backgrounds and susceptibility in Gambian Plasmodium falciparum. Journal of global antimicrobial resistance 2 41985582
2026 Sustained high prevalence of multiple antimalarial drug resistance markers in Uganda in 2023-2024. Antimicrobial agents and chemotherapy 2 42294652
2025 Molecular basis of the functional conflict between chloroquine and peptide transport in the Malaria parasite chloroquine resistance transporter PfCRT. Nature communications 2 40140375
2025 Genetic epidemiology of Plasmodium falciparum chloroquine resistance in coastal, North and Far North areas of Cameroon. Transactions of the Royal Society of Tropical Medicine and Hygiene 2 40635523
2025 A review on molecular markers of Plasmodium falciparum. Journal of parasitic diseases : official organ of the Indian Society for Parasitology 2 41230275
2026 Collateral hypersensitivity between ZY19489 and piperaquine neutralizes PfCRT-mediated drug efflux and Plasmodium falciparum resistance. Nature communications 1 41922323
2026 Plasmodium falciparum Chloroquine Resistance Transporter (PfCRT) Is a Redox-Dependent Drug Transporter. Biochemistry 0 41810826
2026 Geographical Variation in Antimalarial Drug Resistance Marker Prevalence Across the Southern African Elimination Eight Region. medRxiv : the preprint server for health sciences 0 42238473
2026 Droplet digital PCR assays for Pvmdr1 and Pvcrt-o gene copy number variation determination in Plasmodium vivax. Malaria journal 0 42271343
2026 Identification of genetic markers of quinine partial resistance in Plasmodium falciparum. Nature microbiology 0 42410209
2026 Mapping the prevalence of molecular markers of Plasmodium falciparum artemisinin partial resistance in Africa: a systematic review and spatiotemporal modelling study. The Lancet. Infectious diseases 0 42413528
2026 Drug resistance gene polymorphisms of Plasmodium falciparum clinical isolates from Kinshasa, Democratic Republic of the Congo. Tropical medicine and health 0 42415199