title: A process similar to autophagy is associated with cytocidal chloroquine resistance in Plasmodium falciparum.
abstract: Resistance to the cytostatic activity of the antimalarial drug chloroquine (CQ) is becoming well understood, however, resistance to cytocidal effects of CQ is largely unexplored. We find that PfCRT mutations that almost fully recapitulate P. falciparum cytostatic CQ resistance (CQR(CS)) as quantified by CQ IC50 shift, account for only 10-20% of cytocidal CQR (CQR(CC)) as quantified by CQ LD50 shift. Quantitative trait loci (QTL) analysis of the progeny of a chloroquine sensitive (CQS; strain HB3)×chloroquine resistant (CQR; strain Dd2) genetic cross identifies distinct genetic architectures for CQR(CS) vs CQR(CC) phenotypes, including identification of novel interacting chromosomal loci that influence CQ LD50. Candidate genes in these loci are consistent with a role for autophagy in CQR(CC), leading us to directly examine the autophagy pathway in intraerythrocytic CQR parasites. Indirect immunofluorescence of RBC infected with synchronized CQS vs CQR trophozoite stage parasites reveals differences in the distribution of the autophagy marker protein PfATG8 coinciding with CQR(CC). Taken together, the data show that an unusual autophagy-like process is either activated or inhibited for intraerythrocytic trophozoite parasites at LD50 doses (but not IC50 doses) of CQ, that the pathway is altered in CQR P. falciparum, and that it may contribute along with mutations in PfCRT to confer the CQR(CC) phenotype.
authors.affiliation: Departments of Chemistry and of Biochemistry, Cellular and Molecular Biology, Georgetown University, Washington, District of Columbia, United States of America.
authors.forename: David
authors.initials: D
authors.lastname: Gaviria
authors.forename: Michelle F
authors.initials: MF
authors.lastname: Paguio
authors.forename: Lindsey B
authors.initials: LB
authors.lastname: Turnbull
authors.forename: Asako
authors.initials: A
authors.lastname: Tan
authors.forename: Amila
authors.initials: A
authors.lastname: Siriwardana
authors.forename: Debasish
authors.initials: D
authors.lastname: Ghosh
authors.forename: Michael T
authors.initials: MT
authors.lastname: Ferdig
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Sinai
authors.forename: Paul D
authors.initials: PD
authors.lastname: Roepe
mesh_terms: D000962:Antimalarials / Q000494:pharmacology*; D001343:Autophagy / Q000187:drug effects; D002738:Chloroquine / Q000494:pharmacology*; D004351:Drug Resistance; D010963:Plasmodium falciparum / Q000187:drug effects*; D015800:Protozoan Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000962:Antimalarials; D015800:Protozoan Proteins; D002738:Chloroquine