title: Chloroquine resistance not linked to mdr-like genes in a Plasmodium falciparum cross.
abstract: Chloroquine is thought to act against falciparum malaria by accumulating in the acid vesicles of the parasite and interfering with their function. Parasites resistant to chloroquine expel the drug rapidly in an unaltered form, thereby reducing levels of accumulation in the vesicles. The discovery that verapamil partially reverses chloroquine resistance in vitro led to the proposal that efflux may involve an ATP-driven P-glycoprotein pump similar to that in mammalian multidrug-resistant (mdr) tumor cell lines. Indeed, Plasmodium falciparum contains at least two mdr-like genes, one of which has been suggested to confer the chloroquine resistant (CQR) phenotype. To determine if either of these genes is linked to chloroquine resistance, we performed a genetic cross between CQR and chloroquine-susceptible (CQS) clones of P. falciparum. Examination of 16 independent recombinant progeny indicated that the rapid efflux phenotype is controlled by a single gene or a closely linked group of genes. But, there was no linkage between the rapid efflux, CQR phenotype and either of the mdr-like P. falciparum genes or amplification of those genes. These data indicate that the genetic locus governing chloroquine efflux and resistance is independent of the known mdr-like genes.
authors.affiliation: Laboratory of Parasitic Diseases, National Institute of Allergy, Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: T E
authors.initials: TE
authors.lastname: Wellems
authors.forename: L J
authors.initials: LJ
authors.lastname: Panton
authors.forename: I Y
authors.initials: IY
authors.lastname: Gluzman
authors.forename: V E
authors.initials: VE
authors.lastname: do Rosario
authors.forename: R W
authors.initials: RW
authors.lastname: Gwadz
authors.forename: A
authors.initials: A
authors.lastname: Walker-Jonah
authors.forename: D J
authors.initials: DJ
authors.lastname: Krogstad
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000818:Animals; D001483:Base Sequence; D002738:Chloroquine / Q000378:metabolism / Q000494:pharmacology*; D003433:Crosses, Genetic; D004351:Drug Resistance / Q000235:genetics*; D005784:Gene Amplification; D005796:Genes; D008562:Membrane Glycoproteins / Q000235:genetics; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D010641:Phenotype; D010963:Plasmodium falciparum / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D008562:Membrane Glycoproteins; D015345:Oligonucleotide Probes; D002738:Chloroquine; D014700:Verapamil