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Role of hexosamine biosynthesis in Leishmania growth and virulence
Author(s) -
Naderer Thomas,
Wee Edmund,
McConville Malcolm J.
Publication year - 2008
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2008.06314.x
Subject(s) - phagolysosome , biology , amastigote , leishmania , biochemistry , microbiology and biotechnology , glycoconjugate , glycolipid , glycosylation , virulence , leishmania mexicana , macrophage , in vitro , gene , parasite hosting , world wide web , computer science
Summary Leishmania parasites incorporate N‐acetylglucosamine (GlcNAc) into surface‐expressed glycosylphosphatidylinositol (GPI) glycolipids and N‐linked glycans. To investigate whether these glycoconjugates are required for infectivity of promastigote and intracellular amastigote stages, we generated a Leishmania major mutant lacking the gene encoding glutamine : fructose‐6‐phosphate amidotransferase (GFAT). The L. major Δ gfat mutant is unable to synthesize GlcN‐6‐phosphate de novo and is auxotrophic for GlcN or GlcNAc. GlcN starvation leads to the rapid depletion of dolichol‐linked oligosaccharides and GPI precursors, hypersensitivity to elevated temperatures encountered in the mammalian host and eventual parasite death. Short‐term tunicamycin treatment induces a similar hypersensitivity to temperature, indicating that N‐linked glycans are required for thermotolerance and viability. L. major Δ gfat promastigotes are unable to proliferate in ex vivo infected macrophages, demonstrating that GlcN(Ac) levels in the phagolysosome are low. In contrast, Δ gfat amastigotes grow as well as wild‐type amastigotes in macrophages and induce lesions in susceptible mice. These stages still require GlcN(Ac) for viability but can apparently scavenge all of their glucosamine requirements from the macrophage phagolysosome. These results highlight significant differences in the nutrient requirements of promastigote and amastigote stages and suggest that enzymes involved in UDP‐GlcNAc biosynthesis are essential for pathogenesis in the mammalian host.