Leishmania infantum Asparagine Synthetase A Is Dispensable for Parasites Survival and Infectivity

PLoS Negl Trop Dis. 2016 Jan 15;10(1):e0004365. doi: 10.1371/journal.pntd.0004365. eCollection 2016 Jan.

Abstract

A growing interest in asparagine (Asn) metabolism has currently been observed in cancer and infection fields. Asparagine synthetase (AS) is responsible for the conversion of aspartate into Asn in an ATP-dependent manner, using ammonia or glutamine as a nitrogen source. There are two structurally distinct AS: the strictly ammonia dependent, type A, and the type B, which preferably uses glutamine. Absent in humans and present in trypanosomatids, AS-A was worthy of exploring as a potential drug target candidate. Appealingly, it was reported that AS-A was essential in Leishmania donovani, making it a promising drug target. In the work herein we demonstrate that Leishmania infantum AS-A, similarly to Trypanosoma spp. and L. donovani, is able to use both ammonia and glutamine as nitrogen donors. Moreover, we have successfully generated LiASA null mutants by targeted gene replacement in L. infantum, and these parasites do not display any significant growth or infectivity defect. Indeed, a severe impairment of in vitro growth was only observed when null mutants were cultured in asparagine limiting conditions. Altogether our results demonstrate that despite being important under asparagine limitation, LiAS-A is not essential for parasite survival, growth or infectivity in normal in vitro and in vivo conditions. Therefore we exclude AS-A as a suitable drug target against L. infantum parasites.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ammonia / metabolism
  • Animals
  • Asparagine / metabolism
  • Aspartate-Ammonia Ligase / chemistry
  • Aspartate-Ammonia Ligase / genetics
  • Aspartate-Ammonia Ligase / metabolism*
  • Female
  • Glutamine / metabolism
  • Humans
  • Leishmania infantum / enzymology*
  • Leishmania infantum / genetics
  • Leishmania infantum / growth & development
  • Leishmania infantum / pathogenicity*
  • Leishmaniasis, Visceral / parasitology*
  • Mice, Inbred BALB C
  • Molecular Sequence Data
  • Protozoan Proteins / chemistry
  • Protozoan Proteins / genetics
  • Protozoan Proteins / metabolism*
  • Sequence Alignment
  • Virulence

Substances

  • Protozoan Proteins
  • Glutamine
  • Asparagine
  • Ammonia
  • Aspartate-Ammonia Ligase

Grants and funding

The research leading to these results has received funding from: the European Community’s Seventh Framework Programme under grant agreement No.602773 (Project KINDRED) and Fundação para a Ciência e Tecnologia (FCT)/Ministério da Educação e Ciência (MEC) cofunded by FEDER, partnership agreement PT2020, through the Research Unit No.4293. The COST Action CM1307: Targeted chemotherapy towards diseases caused by endoparasites has also contributed to this work. We would like to acknowledge FCT for supporting JF(SFRH/BD/79712/2011) and IL (SFRH/BD/64528/2009). IL was also supported by the European Community’s Seventh Framework Programme (KINDRED-PR300102-BD). JT is an Investigator FCT funded by National funds through FCT and co-funded through European Social Fund within the Human Potential Operating Programme. NS is supported by a fellowship from the European Community’s Seventh Framework Programme under grant agreements No. 602773 (Project KINDRED). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.