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Discovering thiamine transporters as targets of chloroquine using a novel functional genomics strategy.

Chloroquine (CQ) and other quinoline-containing antimalarials are important drugs with many therapeutic benefits as well as adverse effects. However, the molecular targets underlying most such effects are largely unknown. By taking a novel functional genomics strategy, which employs a unique combination of genome-wide drug-gene synthetic lethality (DGSL), gene-gene synthetic lethality (GGSL), and dosage suppression (DS) screens in the model organism Saccharomyces cerevisiae and is thus termed SL/DS for simplicity, we found that CQ inhibits the thiamine transporters Thi7, Nrt1, and Thi72 in yeast. We first discovered a thi3Δ mutant as hypersensitive to CQ using a genome-wide DGSL analysis. Using genome-wide GGSL and DS screens, we then found that a thi7Δ mutation confers severe growth defect in the thi3Δ mutant and that THI7 overexpression suppresses CQ-hypersensitivity of this mutant. We subsequently showed that CQ inhibits the functions of Thi7 and its homologues Nrt1 and Thi72. In particular, the transporter activity of wild-type Thi7 but not a CQ-resistant mutant (Thi7(T287N)) was completely inhibited by the drug. Similar effects were also observed with other quinoline-containing antimalarials. In addition, CQ completely inhibited a human thiamine transporter (SLC19A3) expressed in yeast and significantly inhibited thiamine uptake in cultured human cell lines. Therefore, inhibition of thiamine uptake is a conserved mechanism of action of CQ. This study also demonstrated SL/DS as a uniquely effective methodology for discovering drug targets.

Pubmed ID: 23209439

Authors

  • Huang Z
  • Srinivasan S
  • Zhang J
  • Chen K
  • Li Y
  • Li W
  • Quiocho FA
  • Pan X

Journal

PLoS genetics

Publication Data

December 4, 2012

Associated Grants

  • Agency: NHGRI NIH HHS, Id: HG004840

Mesh Terms

  • Antimalarials
  • Biological Transport
  • Chloroquine
  • Gene Expression
  • Genomics
  • Humans
  • Membrane Transport Proteins
  • Mutation
  • Nucleoside Transport Proteins
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Thiamine