Pyrimidine biosynthesis is not an essential function for trypanosoma brucei bloodstream forms

Ali, J. A.., Tagoe, D. N.A., Munday, J. C. , Donachie, A., Morrison, L. J. and De Koning, H. P. (2013) Pyrimidine biosynthesis is not an essential function for trypanosoma brucei bloodstream forms. PLoS ONE, 8(3), e58034. (doi:10.1371/journal.pone.0058034) (PMID:23505454) (PMCID:PMC3591441)

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Abstract

Background: African trypanosomes are capable of both pyrimidine biosynthesis and salvage of preformed pyrimidines from the host, but it is unknown whether either process is essential to the parasite.

Methodology/Principal Findings: Pyrimidine requirements for growth were investigated using strictly pyrimidine-free media, with or without single added pyrimidine sources. Growth rates of wild-type bloodstream form Trypanosoma brucei brucei were unchanged in pyrimidine-free medium. The essentiality of the de novo pyrimidine biosynthesis pathway was studied by knocking out the PYR6-5 locus that produces a fusion product of orotate phosphoribosyltransferase (OPRT) and Orotidine Monophosphate Decarboxylase (OMPDCase). The pyrimidine auxotroph was dependent on a suitable extracellular pyrimidine source. Pyrimidine starvation was rapidly lethal and non-reversible, causing incomplete DNA content in new cells. The phenotype could be rescued by addition of uracil; supplementation with uridine, 2′deoxyuridine, and cytidine allowed a diminished growth rate and density. PYR6-5−/− trypanosomes were more sensitive to pyrimidine antimetabolites and displayed increased uracil transport rates and uridine phosphorylase activity. Pyrimidine auxotrophs were able to infect mice although the infection developed much more slowly than infection with the parental, prototrophic trypanosome line.

Conclusions/Significance: Pyrimidine salvage was not an essential function for bloodstream T. b. brucei. However, trypanosomes lacking de novo pyrimidine biosynthesis are completely dependent on an extracellular pyrimidine source, strongly preferring uracil, and display reduced infectivity. As T. brucei are able to salvage sufficient pyrimidines from the host environment, the pyrimidine biosynthesis pathway is not a viable drug target, although any interruption of pyrimidine supply was lethal.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Munday, Dr Jane and De Koning, Professor Harry and Donachie, Ms Anne Marie and Morrison, Dr Liam
Authors: Ali, J. A.., Tagoe, D. N.A., Munday, J. C., Donachie, A., Morrison, L. J., and De Koning, H. P.
College/School:College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
Journal Name:PLoS ONE
Publisher:Public Library of Science
ISSN:1932-6203
ISSN (Online):1932-6203
Copyright Holders:Copyright © 2013 The Authors
First Published:First published in PLoS ONE 8(3):e58034
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
371796The Wellcome Centre for Molecular Parasitology ( Core Support )Andrew WatersWellcome Trust (WELLCOME)085349/Z/08/ZIII - PARASITOLOGY
371798The Wellcome Centre for Molecular Parasitology ( Core Support )Andrew WatersWellcome Trust (WELLCOME)085349/B/08/ZIII - PARASITOLOGY