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GMP synthase is essential for viability and infectivity of T rypanosoma brucei despite a redundant purine salvage pathway
Author(s) -
Li Qiong,
Leija Christopher,
RijoFerreira Filipa,
Chen Jun,
Cestari Igor,
Stuart Kenneth,
Tu Benjamin P.,
Phillips Margaret A.
Publication year - 2015
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/mmi.13083
Subject(s) - biology , hypoxanthine guanine phosphoribosyltransferase , nucleotide salvage , trypanosoma brucei , hypoxanthine , biochemistry , purine nucleoside phosphorylase , purine metabolism , purine , guanosine monophosphate , phosphoribosyltransferase , nucleotide , mutant , enzyme , gene
Summary The causative agent of human African trypanosomiasis, T rypanosoma brucei , lacks de novo purine biosynthesis and depends on purine salvage from the host. The purine salvage pathway is redundant and contains two routes to guanosine‐5′‐monophosphate ( GMP ) formation: conversion from xanthosine‐5′‐monophosphate ( XMP ) by GMP synthase ( GMPS ) or direct salvage of guanine by hypoxanthine‐guanine phosphoribosyltransferase ( HGPRT ). We show recombinant T . brucei GMPS efficiently catalyzes GMP formation. Genetic knockout of GMPS in bloodstream parasites led to depletion of guanine nucleotide pools and was lethal. Growth of gmps null cells was only rescued by supraphysiological guanine concentrations (100 μM) or by expression of an extrachromosomal copy of GMPS . Hypoxanthine was a competitive inhibitor of guanine rescue, consistent with a common uptake/metabolic conversion mechanism. In mice, gmps null parasites were unable to establish an infection demonstrating that GMPS is essential for virulence and that plasma guanine is insufficient to support parasite purine requirements. These data validate GMPS as a potential therapeutic target for treatment of human A frican trypanosomiasis. The ability to strategically inhibit key metabolic enzymes in the purine pathway unexpectedly bypasses its functional redundancy by exploiting both the nature of pathway flux and the limited nutrient environment of the parasite's extracellular niche.