Galactose Starvation in a Bloodstream Form
            <i>Trypanosoma brucei</i>
            UDP-Glucose 4′-Epimerase Conditional Null Mutant

Urbaniak, Michael D.; Turnock, Daniel C.; Ferguson, Michael A. J.

doi:10.1128/ec.00156-06

Cited by 42 publications

(61 citation statements)

References 23 publications

(34 reference statements)

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“…For these reasons, we believe that the MRM method is a good tool for detecting and quantifying low-abundance sugar nucleotides, such as UDP-Galf, UDP-Xyl, GDP-Ara, and GDP-Fuc, from relatively small culture volumes (10 to 100 ml). The method has already proved useful in characterizing sugar nucleotide levels for two UDP-Gal 4Ј-epimerase-deficient cell lines (62,120) and will be applied to other trypanosome mutants to monitor the effects on sugar nucleotide levels.…”

Section: Discussionmentioning

confidence: 99%

“…The only route to UDP-Galp in bloodstream and procyclic-form T. brucei and epimastigote form T. cruzi is via the epimerization of UDPGlc, because their hexose transporters are unable to transport Gal (9,112). The UDP-Glc 4Ј-epimerase (GalE) responsible for this interconversion is essential in both life cycle stages of T. brucei (96,97,120) and appears to be essential for T. cruzi epimastigotes (62), suggesting that this enzyme may be a good therapeutic target against African trypanosomiasis and possibly Chagas' disease.…”

Section: Cruzi) Gdp-man Is Also the Precursor Of Gdp-fuc (See Below)mentioning

confidence: 99%

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Sugar Nucleotide Pools of Trypanosoma brucei , Trypanosoma cruzi , and Leishmania major

2007

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The cell surface glycoconjugates of trypanosomatid parasites are intimately involved in parasite survival, infectivity, and virulence in their insect vectors and mammalian hosts. Although there is a considerable body of work describing their structure, biosynthesis, and function, little is known about the sugar nucleotide pools that fuel their biosynthesis. In order to identify and quantify parasite sugar nucleotides, we developed an analytical method based on liquid chromatography-electrospray ionization-tandem mass spectrometry using multiple reaction monitoring. This method was applied to the bloodstream and procyclic forms of Trypanosoma brucei, the epimastigote form of T. cruzi, and the promastigote form of Leishmania major. The trypanosomatids are protozoan parasites that impose a major health burden on many countries in the developing world, causing a wide range of diseases over three continents. Like most eukaryotes, the cell surfaces and endosomal/lysosomal systems of these organisms are rich in glycoconjugates, some of which play essential roles in their survival, infectivity, or virulence. The glycoconjugate repertoires of the three trypanosomatids studied here, Trypanosoma brucei, T. cruzi, and Leishmania major, are fundamentally different, reflecting their disparate life cycles, modes of infection, and disease pathologies (see references 5,27,28,38,47,65, and 69 and references therein). The monosaccharides that make up these glycoconjugates vary between the three trypanosomatid species. For example, all three contain D-mannose (Man), D-Nacetylglucosamine (GlcNAc), D-glucosamine (GlcN), D-glucose (Glc), and D-galactopyranose (Galp), while only T. cruzi and L. major contain D-galactofuranose (Galf), only T. cruzi contains D-xylose (Xyl), L-rhamnopyranose (Rha), and L-fucose (Fuc), and only L. major contains D-arabinopyranose (Ara) ( Table 1). However, a unifying theme of their glycobiology is an abundance of cell surface glycosylphosphatidylinositol (GPI)-anchored glycoproteins and/or non-proteinlinked GPI structures.The protein-linked GPI glycans of the leishmania are the simplest in structure, consisting of the conserved Man␣1-2Man␣1-6Man␣1-4GlcN core. Those of T. cruzi are principally Man␣1-2Man␣1-2Man␣1-6Man␣1-4GlcN, and those of T. brucei are the most complex, with ␣-D-Galp and ␤-D-Galp side chains in the bloodstream form and sialylated poly-N-acetyllactosamine (poly-LacNAc) side chains in the procyclic form (27).The non-protein-linked GPI structures include the so-called glycoinositolphospholipids, or GIPLs, that are most abundant in the leishmania and T. cruzi species (58, 64, 90) but are also found in procyclic-form T. brucei (60,73,122) and bloodstream form T. brucei (39,63). Non-protein-linked GPIs also include the more exotic leishmania-specific lipophosphoglycan (LPG) structures (38,47,64,65). The leishmania LPGs contain characteristic phosphosaccharide repeats of Galp␤1-4Man␣1-P, which in L. major can have ␤-D-Galp and ␣-D-Arap side chains (66,67). These repeats are also found in the secr...

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Section: Discussionmentioning

confidence: 99%

Section: Cruzi) Gdp-man Is Also the Precursor Of Gdp-fuc (See Below)mentioning

confidence: 99%

Sugar Nucleotide Pools of Trypanosoma brucei , Trypanosoma cruzi , and Leishmania major

2007

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“…This may explain why GalNAc has yet to be found in any glycoconjugates of this parasite. (b) All the enzymes identified in the biosynthesis of the above five nucleotide sugars were localized to the glycosomes (44,46,59,(61)(62)(63), which are microbodies evolutionarily related to peroxisomes in higher eukaryotes and their function is essential in carbohydrate metabolism in T. brucei. However, in its mammalian hosts, most nucleotide sugars are synthesized in the cytosol.…”

Section: Discussionmentioning

confidence: 99%

“…Previous studies have shown that enzymes involved in nucleotide sugar biosynthesis in T. brucei such as UDP-Gal (59,61,78), GDP-Fuc (62), GlcNAc (63), and GDP-Man are essential for cell growth, but none of them were shown to cause pathogenicity changes in BSF T. brucei. We speculate that the function of the totality of TbNSTs is essential for cell growth and that inhibition of a specific or multiple tbnst involved in glycosylation of essential proteins for virulence will change the parasites' infectivity.…”

Section: Discussionmentioning

confidence: 99%

Inhibition of Nucleotide Sugar Transport in Trypanosoma brucei Alters Surface Glycosylation

Liu

Caradonna

et al. 2013

Journal of Biological Chemistry

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Background: Nucleotide sugar transporters (NSTs) provide availability of nucleotide sugars for glycosylation in the lumen of the Golgi apparatus. Results: The substrate specificities of four Trypanosoma brucei NSTs were characterized, and inhibition of TbNST4 resulted in glycosylation defects. Conclusion: TbNST4 plays an essential role in biosynthesis of glycoproteins in T. brucei. Significance: To understand the roles of TbNST(s) in the growth and pathogenesis of T. brucei.

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“…This pathway is essential in unicellular parasites from the genus Trypanosoma since they are unable to take up galactose from the environment and rely on "reversing" some of the Leloir pathway reactions in order to generate galactose for glycoprotein synthesis [207][208][209][210][211]. Thus, inhibition of GALE in these species has potential for the development of novel therapeutics [212][213][214][215].…”

Section: Other Metabolic Pathwaysmentioning

confidence: 99%

Metabolic enzymes of helminth parasites: potential as drug targets

Timson¹

2015

CPPS

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Metabolic pathways which extract energy from carbon compounds are essential for an organism's survival. Therefore, inhibition of enzymes in these pathways represents a potential therapeutic strategy to combat parasitic infections. However, the high degree of similarity between host and parasite enzymes makes this strategy potentially difficult. Nevertheless, several existing drugs to treat infections by parasitic helminths (worms) target metabolic enzymes. These include the trivalent antimonials which target phosphofructokinase and Clorsulon which targets phosphoglycerate mutase and phosphoglycerate kinase. Glycolytic enzymes from a variety of helminths have been characterised biochemically, and some inhibitors identified. To date none of these inhibitors have been developed into therapies. Many of these enzymes are externalised from the parasite and so are also of interest in the development of potential vaccines. Less work has been done on tricarboxylic acid cycle enzymes and oxidative phosphorylation complexes. Again, while some inhibitors have been identified none have been developed into drug-like molecules. Barriers to the development of novel drugs targeting metabolic enzymes include the lack of experimentally determined structures of helminth enzymes, lack of direct proof that the enzymes are vital in the parasites and lack of cell culture systems for many helminth species. Nevertheless, the success of Clorsulon (which discriminates between highly similar host and parasite enzymes) should inspire us to consider making serious efforts to discover novel anthelminthics which target metabolic enzymes.

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Galactose Starvation in a Bloodstream Form Trypanosoma brucei UDP-Glucose 4′-Epimerase Conditional Null Mutant

Cited by 42 publications

References 23 publications

Sugar Nucleotide Pools of Trypanosoma brucei , Trypanosoma cruzi , and Leishmania major

Sugar Nucleotide Pools of Trypanosoma brucei , Trypanosoma cruzi , and Leishmania major

Inhibition of Nucleotide Sugar Transport in Trypanosoma brucei Alters Surface Glycosylation

Metabolic enzymes of helminth parasites: potential as drug targets

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