PTR1-dependent synthesis of tetrahydrobiopterin contributes to oxidant susceptibility in the trypanosomatid protozoan parasite Leishmania major

Bakela Nare, Levi A. Garraway, Tim J. Vickers, Stephen M. Beverley

Research output: Contribution to journalReview articlepeer-review

28 Scopus citations

Abstract

Leishmania must survive oxidative stress, but lack many classical antioxidant enzymes and rely heavily on trypanothione-dependent pathways. We used forward genetic screens to recover loci mediating oxidant resistance via overexpression in Leishmania major, which identified pteridine reductase 1 (PTR1). Comparisons of isogenic lines showed ptr1- null mutants were 18-fold more sensitive to H2O2 than PTR1-overproducing lines, and significant three- to fivefold differences were seen with a broad panel of oxidant-inducing agents. The toxicities of simple nitric oxide generators and other drug classes (except antifolates) were unaffected by PTR1 levels. H2O2 susceptibility could be modulated by exogenous biopterin but not folate, in a PTR1- but not dihydrofolate reductase-dependent manner, implicating H4B metabolism specifically. Neither H2O2 consumption nor the level of intracellular oxidative stress was affected by PTR1 levels. Coupled with the fact that reduced pteridines are at least 100-fold less abundant than cellular thiols, these data argue strongly that reduced pteridines act through a mechanism other than scavenging. The ability of unconjugated pteridines to counter oxidative stress has implications to infectivity and response to chemotherapy. Since the intracellular pteridine levels of Leishmania can be readily manipulated, these organisms offer a powerful setting for the dissection of pteridine-dependent oxidant susceptibility in higher eukaryotes.

Original languageEnglish
Pages (from-to)287-299
Number of pages13
JournalCurrent Genetics
Volume55
Issue number3
DOIs
StatePublished - 2009

Keywords

  • Folates
  • Forward genetics
  • Hydrogen peroxide
  • Nitric oxide
  • Pteridines
  • Trypanothione

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