MOLECULAR GLYCOBIOLOGY AT THE BOKU
Department für Chemie
Universität für Bodenkultur
Muthgasse 18, A-1190 Wien
Dipl-Ing. Barbara Eckmair (barbara.eckmair(at)boku.ac.at)
Denise Kerner (denise.kerner(at)boku.ac.at)
Major research interests:
Functional and Medical Glycobiology and Glycomics
Glycans are a code which modifies the function of the proteins or lipids to which they are attached; this code is first generated by glycosyltransferases and glycosidases and must then be read by carbohydrate binding proteins (such as antibodies or lectins) in order to have any function. Much of our work has the aim of understanding the structure, biosynthesis, function and medical repercussions of glycosylation.
Specifically ongoing projects on the glycogenomics of Caenorhabditis elegans (P23922) and Aspergillus fumigatus (I391) as well as projects on comparative glycomics of nematodes and Echinodermata (FWF Projects P21946 and P25058, led by Dr. Katharina Paschinger) seek to correlate glycosylation with actual function; a new grant on the development of glycan arrays (P23607) has the goal, in collaboration with Prof. Kosma, of developing new chemical glycobiological tools, whereas a Translational Research Project (TRP127, led by Dr. Dubravko Rendic) is focussed on preparation of recombinant glycosidases. Furthermore, the group is a member of the GlycoPar Initial Training Network (www.glycopar.eu). We publish in leading biochemical journals and many of our previous diploma and block students have been co-authors on our papers.
Glycobiology of model organisms
The sequencing of the genomes of multicellular organisms has shown that 1% of all genes are directly relevant to glycoconjugate metabolism. Over the years we have cloned cDNAs encoding a number of glycosyltransferases from Arabidopsis thaliana, rice, Caenorhabditis elegans and Drosophila melanogaster with a particular focus on fucosyltransferases (see, e.g., J. Biol. Chem., 276, 28058-67, J. Biol. Chem., 279, 49588-98, J. Biol. Chem., 281, 3343-53 and J. Biol. Chem. 288, 21015-28). These enzymes catalyse the attachment of fucose to glycans – in particular we have focused on those modifying the N-glycan core region; they can then be used as tools for generating fucosylated glycans in vitro.
Fucose is a sugar which is often associated with recognition events – such as selectin-mediated interactions during inflammatory responses. In the context of plant glycosylation, core α1,3-fucose is present on many allergens and is immunogenic; in Caenorhabditis and Drosophila the same structure is present in neuronal tissue. Indeed antibodies raised against a plant glycoprotein, horseradish peroxidase (HRP), recognise neural tissue in many invertebrates. In order to define which fucosyltransferases are responsible in vivo for the formation of this anti-HRP epitope, we have performed glycan analysis of mutant Caenorhabditis and used RNAi in a Drosophila neural cell line. A mix of biochemical and genetic approaches is now being used to examine glycosylation in Dictyostelium discoideum (Biochem. J., 423, 41-52 and J. Prot. Res. 12, 1173-87).
Complementary to the study of fucosyltransferases is the examination of the enzymes responsible for making the fucose donor, GDP-Fucose, and other enzymes (such as hexosaminidases) which play roles in glycan biosynthesis. In the mouse, we have uncovered a novel hexosaminidase (HexD; Biochem. J., 419, 83-90) and also examined the closest worm relatives of HexD using a range of techniques (J. Biol. Chem., 282, 27825-40 and J. Biol. Chem., 287, 28276–90). We also examined the Golgi mannosidase II from Caenorhabditis (J. Biol. Chem., 281, 28265-77) which is a key enzyme for normal N-glycan biosynthesis not just in worms but also in mammals.
We use a wide range of tools in order to examine the glycosylation of model organisms – naturally normal molecular biology methods such as cloning of cDNAs and expression of glycosyltransferases in yeast (specifically Pichia) and in insect cells; GDP-Fucose synthesising enzymes have been expressed in E. coli (see FEBS Journal, 273, 2244-56). Enzymological characterisation, RNAi in cell culture, generation of specific substrates and analysis of glycans from plants and invertebrates (by HPLC and MALDI-TOF MS) complete the in-house methodological palette. We also grow our own wild-type and mutant worms and flies. Also, we have exploited some of the recombinant glycosyltransferases in our lab in order to make neoglycoforms of transferrin so that we can determine lectin specificities (Anal. Biochem., 386, 133-46) as well as generate nematode-type trifucosylated N-glycan cores (J. Biol. Chem. 288, 21015-28).
Glyco-Allergology and Glyco-Parasitology
The differences in glycosylation between humans and other organisms are often associated with immunological responses – many plant glycoproteins carry core α1,3-fucose. This constitutes an epitope for IgE and we have analysed allergens for collaborators such as cypress pollen allergen (Allergy, 56, 978-84), a major kiwifruit allergen (FASEB J., 17, 1697-99) and an orange allergen (Glycobiology, 17, 220-230). Some of these developments are summarised in a review in Acta Biochimica Polonica, 52, 629-32. Furthermore, it is interesting that allergy is often more prevalent in regions where helminth parasite infestation is not endemic. Often helminth glycans carry fucose residues; an example being those of Schistosoma mansoni. We have characterised fucosyltransferase activities in this parasite (see Eur J Immunol, 33, 1271-81, and Glycobiology, 15, 463-74) and have performed similar studies on the pig parasite Ascaris suum (FEBS J., 274, 714-726). Most recently, we have analysed the N-glycans of Trichomonas vaginalis (Glycobiology, 22, 300-313), of Echinococcus granulosus (Int. J. Parasitol, 42, 279–285) and of Acanthamoeba (J. Biol. Chem., 287, 43191–204). This approach will be extended in the future with a view to aiding understanding of immune response to helminths by generating relevant glycan reagents.
Movies and Images
For movies and images, please refer to the "Movies and Images" section.
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