Leishmania mexicana can utilize amino acids as major carbon sources in macrophages but not in animal models

5 years ago

Leishmania mexicana can utilize amino acids as major carbon sources in macrophages but not in animal models

Malcolm J. McConville, Eleanor C. Saunders, Scott M. Landfear, Jenny Chambers, Thomas Naderer

Leishmania parasites target macrophages in their mammalian hosts and proliferate within the mature phagolysosome compartment of these cells. Intracellular amastigote stages are dependent on sugars as a major carbon source in vivo, but retain the capacity to utilize other carbon sources. To investigate whether amastigotes can switch to using other carbon sources, we have screened for suppressor strains of the L. mexicana Δlmxgt1-3 mutant which lacks the major glucose transporters LmxGT1-3. We identified a novel suppressor line (Δlmxgt1-3s2) that has restored growth in rich culture medium and virulence in ex vivo infected macrophages, but failed to induce lesions in mice. Δlmxgt1-3s2 amastigotes had lower rates of glucose utilization than the parental line and primarily catabolized non-essential amino acids. The increased mitochondrial metabolism of this line was associated with elevated levels of intracellular reactive oxygen species, as well as increased sensitivity to inhibitors of the tricarboxylic acid (TCA) cycle, including nitric oxide. These results suggest that hardwired sugar addiction of Leishmania amastigotes contributes to the intrinsic resistance of this stage to macrophage microbicidal processes in vivo, and that these stages have limited capacity to switch to using other carbon sources. This article is protected by copyright. All rights reserved. Leishmania parasites target macrophages and other immune cells in their animal host and reside within a nutrient-rich lysosomal compartment. Here we show that intracellular parasites are addicted to using sugars as their major carbon source as utilization of other nutrients (amino acids) leads to increased sensitivity to host anti-microbial responses. These findings indicate that resistance to drugs that target sugar metabolism will be slow to evolve.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/mmi.13923