title: Leishmania major UDP-sugar pyrophosphorylase salvages galactose for glycoconjugate biosynthesis.
abstract: Leishmaniases are a set of tropical and sub-tropical diseases caused by protozoan parasites of the genus Leishmania whose severity ranges from self-healing cutaneous lesions to fatal visceral infections. Leishmania parasites synthesise a wide array of cell surface and secreted glycoconjugates that play important roles in infection. These glycoconjugates are particularly abundant in the promastigote form and known to be essential for establishment of infection in the insect midgut and effective transmission to the mammalian host. Since they are rich in galactose, their biosynthesis requires an ample supply of UDP-galactose. This nucleotide-sugar arises from epimerisation of UDP-glucose but also from an uncharacterised galactose salvage pathway. In this study, we evaluated the role of the newly characterised UDP-sugar pyrophosphorylase (USP) of Leishmania major in UDP-galactose biosynthesis. Upon deletion of the USP encoding gene, L. major lost the ability to synthesise UDP-galactose from galactose-1-phosphate but its ability to convert glucose-1-phosphate into UDP-glucose was fully maintained. Thus USP plays a role in UDP-galactose activation but does not significantly contribute to the de novo synthesis of UDP-glucose. Accordingly, USP was shown to be dispensable for growth and glycoconjugate biosynthesis under standard growth conditions. However, in a mutant seriously impaired in the de novo synthesis of UDP-galactose (due to deficiency of the UDP-glucose pyrophosphorylase) addition of extracellular galactose increased biosynthesis of the cell surface lipophosphoglycan. Thus under restrictive conditions, such as those encountered by Leishmania in its natural habitat, galactose salvage by USP may play a substantial role in biosynthesis of the UDP-galactose pool. We hypothesise that USP recycles galactose from the blood meal within the midgut of the insect for synthesis of the promastigote glycocalyx and thereby contributes to successful vector infection.
authors.affiliation: Hannover Medical School, Department of Cellular Chemistry OE4330, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Damerow
authors.affiliation: Hannover Medical School, Department of Cellular Chemistry OE4330, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.
authors.forename: Carolin
authors.initials: C
authors.lastname: Hoppe
authors.affiliation: Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom.
authors.forename: Giulia
authors.initials: G
authors.lastname: Bandini
authors.affiliation: Hannover Medical School, Department of Cellular Chemistry OE4330, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.
authors.forename: Patricia
authors.initials: P
authors.lastname: Zarnovican
authors.affiliation: Hannover Medical School, Department of Cellular Chemistry OE4330, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.
authors.forename: Falk F R
authors.initials: FF
authors.lastname: Buettner
authors.affiliation: Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom.
authors.forename: Michael A J
authors.initials: MA
authors.lastname: Ferguson
authors.affiliation: Hannover Medical School, Department of Cellular Chemistry OE4330, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany. Electronic address: Routier.Francoise@mh-hannover.de.
authors.forename: Françoise H
authors.initials: FH
authors.lastname: Routier
mesh_terms: D005690:Galactose / Q000378:metabolism*; D017353:Gene Deletion; D006001:Glycoconjugates / Q000378:metabolism*; D018320:Leishmania major / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase / Q000235:genetics / Q000378:metabolism*; D005694:UTP-Hexose-1-Phosphate Uridylyltransferase / Q000235:genetics / Q000378:metabolism*; D014539:Uridine Diphosphate Sugars / Q000378:metabolism*
chemical_list: D006001:Glycoconjugates; D014539:Uridine Diphosphate Sugars; D005694:UTP-Hexose-1-Phosphate Uridylyltransferase; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase; D005690:Galactose
keywords: Galactose metabolism; Galactose salvage; Glycoconjugates; Leishmania; Nucleotide-sugar; Trypanosomatid