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Molecular and Cellular Biology, December 2001, p. 8168-8183, Vol. 21, No. 23
Max-Planck-Institut für Biologie,
Abteilung Membranbiochemie, 72076 Tübingen, Federal Republic of
Germany,1 and the Division of
Molecular Parasitology & Biological Chemistry, Wellcome Trust
Biocentre, University of Dundee, DD1 4HN Dundee, Scotland, United
Kingdom2
Received 27 June 2001/Accepted 5 September 2001
Leishmania parasites synthesize an abundance
of mannose (Man)-containing glycoconjugates thought to be
essential for virulence to the mammalian host and for viability. These
glycoconjugates include lipophosphoglycan (LPG), proteophosphoglycans
(PPGs), glycosylphosphatidylinositol (GPI)-anchored proteins,
glycoinositolphospholipids (GIPLs), and N-glycans. A prerequisite
for their biosynthesis is an ample supply of the Man donors GDP-Man and
dolicholphosphate-Man. We have cloned from Leishmania
mexicana the gene encoding the enzyme phosphomannomutase
(PMM) and the previously described dolicholphosphate-Man synthase gene (DPMS) that are involved in Man
activation. Surprisingly, gene deletion experiments resulted in viable
parasite lines lacking the respective open reading frames
(
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.23.8168-8183.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Glycosylation Defects and Virulence Phenotypes of
Leishmania mexicana Phosphomannomutase and
Dolicholphosphate-Mannose Synthase Gene Deletion Mutants
PMM and
DPMS), a result against
expectation and in contrast to the lethal phenotype observed in gene
deletion experiments with fungi. L. mexicana
DPMS exhibits a selective defect in LPG, protein GPI
anchor, and GIPL biosynthesis, but despite the absence of these
structures, which have been implicated in parasite virulence and
viability, the mutant remains infectious to macrophages and mice. By
contrast, L. mexicana
PMM are largely devoid of all known Man-containing glycoconjugates and are unable to
establish an infection in mouse macrophages or the living animal. Our
results define Man activation leading to GDP-Man as a virulence pathway
in Leishmania.
*
Corresponding author. Mailing address:
Max-Planck-Institut für Biologie, Abteilung Membranbiochemie,
Corrensstrasse 38, 72076 Tübingen, Federal Republic of Germany.
Phone: 49-7071-601238. Fax: 49-7071-601235. E-mail:
thomas.ilg{at}tuebingen.mpg.de.
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