Arginine sensing in Leishmania

ABSTRACT: Abstract Protozoa of the genus Leishmania are the causative agents of leishmaniasis in humans. These parasites cycle between promastigotes in the sand fly mid-gut and amastigotes in phagolysosome of mammalian macrophages. During infection, they up-regulate host nitric oxide synthase and arginase expression, both of which use arginine as a substrate. These elevated activities deplete macrophage arginine pools, a situation that invading Leishmania must overcome since it is an essential amino acid. Leishmania donovani imports exogenous arginine via a mono-specific amino acid transporter (AAP3) and utilizes it primarily through the polyamine pathway to provide precursors for trypanothione biosynthesis. Here we report the discovery of a pathway whereby promastigote and amastigote forms of the Leishmania sense the lack of environmental arginine and respond with rapid up-regulation in AAP3 expression and activity, as well as several other transporters. Significantly, this arginine deprivation response is also activated in parasites during macrophage infection. Phosphoproteomic analyses of L. donovani promastigotes have implicated a mitogen activated protein kinase 2 (MPK2)-mediated signaling cascade in this response and L. mexicana mutants lacking MPK2 are unable to respond to arginine deprivation. In addition, these mutants cannot differentiate into amastigotes in axenic culture or in peritoneal macrophages, and fail to establish an infection in mice. We propose that sensing arginine levels plays a critical role in Leishmania virulence by activating a rapid metabolic reaction for salvaging this amino acid in response to the lower arginine concentration in the macrophage phagolysosome.

INSTRUMENT(S): LTQ Orbitrap

ORGANISM(S): Leishmania Donovani

SUBMITTER: Keren Bendalak  

LAB HEAD: Dan Zilberstein

PROVIDER: PXD002766 | Pride | 2016-02-17

REPOSITORIES: Pride