Point mutations within the LdNT2 nucleoside transporter gene from Leishmania donovani confer drug resistance and transport deficiency

Jon Galazka, Nicola Carter, Sabih Bekhouche, Shirin Arastu-Kapur, Buddy Ullman

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Leishmania donovani, a protozoan parasite, expresses an unusual inosine/guanosine-specific transporter, LdNT2, the gene for which was cloned by functional rescue of a drug-resistant, LdNT2-deficient (FBD5) strain. In this investigation, we have uncovered and characterized the mutations within the LdNT2 open reading frame that are the basis for the drug-resistance and transport-incompetent phenotype of the FBD5 line. The FBD5 cells were shown to be compound heterozygotes in which both mutant ldnt2 alleles harbor discrete point mutations, each of which impaired transport function and conferred resistance to formycin B, the drug to which the clonal FBD5 line was selected. One of the mutant ldnt2 alleles encoded an S189L alteration in predicted transmembrane domain 5, while the second allele accommodated a null mutation at codon 376, which truncated the transporter just prior to transmembrane domain 8. In addition to the null transport phenotype, very little S189L ldnt2 mutant transporter targeted to the surface of the parasite. The bulk of the truncated ldnt2 appeared to be sequestered internally, possibly within the endoplasmic reticulum, but some of the truncated transporter seemed to be cell surface exposed. The ability to dissect mutations within a viable parasite offers LdNT2 as an attractive model for implementing a thorough forward genetic dissection of transporter function in a eukaryotic cell.

Original languageEnglish (US)
Pages (from-to)1221-1229
Number of pages9
JournalInternational Journal of Biochemistry and Cell Biology
Volume38
Issue number7
DOIs
StatePublished - 2006

Fingerprint

Nucleoside Transport Proteins
Leishmania donovani
Point Mutation
Drug Resistance
Parasites
Genes
Alleles
Mutation
Drug Repositioning
Pharmaceutical Preparations
Phenotype
Dissection
Inosine
Guanosine
Eukaryotic Cells
Heterozygote
Ports and harbors
Codon
Endoplasmic Reticulum
Open Reading Frames

Keywords

  • Genetics
  • Leishmania
  • Nucleosides
  • Purines
  • Transporter

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology

Cite this

Point mutations within the LdNT2 nucleoside transporter gene from Leishmania donovani confer drug resistance and transport deficiency. / Galazka, Jon; Carter, Nicola; Bekhouche, Sabih; Arastu-Kapur, Shirin; Ullman, Buddy.

In: International Journal of Biochemistry and Cell Biology, Vol. 38, No. 7, 2006, p. 1221-1229.

Research output: Contribution to journalArticle

Galazka, Jon ; Carter, Nicola ; Bekhouche, Sabih ; Arastu-Kapur, Shirin ; Ullman, Buddy. / Point mutations within the LdNT2 nucleoside transporter gene from Leishmania donovani confer drug resistance and transport deficiency. In: International Journal of Biochemistry and Cell Biology. 2006 ; Vol. 38, No. 7. pp. 1221-1229.
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