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Designing nanomolar antagonists of DC-SIGN-mediated HIV infection: ligand presentation using molecular rods

Authors: Stefania Ordanini, Norbert Varga, Vanessa Porkolab, Michel Thépaut, Laura Belvisi, Andrea Bertaglia, Alessandro Palmioli, Angela Berzi, Daria Trabattoni, Mario Clerici, Franck Fieschi and Anna Bernardi

Journal: Chem. Commun., 2015, 51, 3816

 

Abstract
DC-SIGN antagonists were designed combining one selective monovalent glycomimetic ligand with trivalent dendrons separated by a rigid core of controlled length. The design combines multiple multivalency effects to achieve inhibitors of HIV infection, which are active in nanomolar concentration.

Synthesis and Microarray-Assisted Binding Studies of Core Xylose and Fucose Containing N‑Glycans

Authors: Katarzyna Brzezicka, Begoña Echeverria, Sonia Serna, Angela van Diepen, Cornelis H. Hokke, and Niels-Christian Reichardt
Journal: ACS Chem. Biol. 2015 DOI: 10.1021/cb501023u

 

Abstract
The synthesis of a collection of 33 xylosylated and core-fucosylated N-glycans found only in nonmammalian organisms such as plants and parasitic helminths has been achieved by employing a highly convergent chemo-enzymatic approach. The influence of these core modifications on the interaction with plant lectins, with the human lectin DC-SIGN (Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Nonintegrin), and with serum antibodies from schistosomeinfected individuals was studied. Core xylosylation markedly reduced or completely abolished binding to several mannosebinding plant lectins and to DC-SIGN, a C-type lectin receptor present on antigen presenting cells. Employing the synthetic collection of core-fucosylated and core-xylosylated N-glycans in the context of a larger glycan array including structures lacking these core modifications, we were able to dissect core xylose and core fucose specific antiglycan antibody responses in S. mansoni infection sera, and we observed clear and immunologically relevant differences between children and adult groups infected with this parasite. The work presented here suggests that, quite similar to bisecting N-acetylglucosamine, core xylose distorts the conformation of the unsubstituted glycan, with important implications for the immunogenicity and protein binding properties of complex N-glycans. DC-SIGN antagonists were designed combining one selective monovalent glycomimetic ligand with trivalent dendrons separated by a rigid core of controlled length. The design combines multiple multivalency effects to achieve inhibitors of HIV infection, which are active in nanomolar concentration.

Discrimination of epimeric glycans and glycopeptides using IM-MS and its potential for carbohydrate sequencing

Authors: P. Both, A. P. Green, C. J. Gray, R. Šardzík, J. Voglmeir, C. Fontana, M. Austeri, M. Rejzek, D. Richardson, R. A. Field, G. Widmalm, S. L. Flitsch, & C. E. Eyers
Journal reference: Nature Chemistry, 6,65–74, (2014) doi:10.1038/nchem.1817

 

Abstract
Mass spectrometry is the primary analytical technique used to characterize the complex oligosaccharides that decorate cell surfaces. Monosaccharide building blocks are often simple epimers, which when combined produce diastereomeric glycoconjugates indistinguishable by mass spectrometry. Structure elucidation frequently relies on assumptions that biosynthetic pathways are highly conserved. Here, we show that biosynthetic enzymes can display unexpected promiscuity, with human glycosyltransferase pp-α-GanT2 able to utilize both uridine diphosphate N-acetylglucosamine and uridine diphosphate N-acetylgalactosamine, leading to the synthesis of epimeric glycopeptides in vitro. Ion-mobility mass spectrometry (IM-MS) was used to separate these structures and, significantly, enabled characterization of the attached glycan based on the drift times of the monosaccharide product ions generated following collision-induced dissociation. Finally, ion-mobility mass spectrometry following fragmentation was used to determine the nature of both the reducing and non-reducing glycans of a series of epimeric disaccharides and the branched pentasaccharide Man3 glycan, demonstrating that this technique may prove useful for the sequencing of complex oligosaccharides.

Glycofullerenes Inhibit Viral Infection

Authors: Joanna Luczkowiak, Antonio Muñoz, Macarena Sánchez-Navarro, Renato Ribeiro-Viana, Anthony Ginieis, Beatriz M. Illescas, Nazario Martín, Rafael Delgado, Javier Rojo
Journal reference: Biomacromolecules 2013, 14, 431−434; DOI: 10.1021/bm3016658

 

Abstract
Water-soluble glycofullerenes based on a hexakis-adduct of [60]fullerene with an octahedral addition pattern are very attractive compounds providing a spherical presentation of carbohydrates. These tools have been recently described and they have been used to interact with lectins in a multivalent manner. Here, we present the use of these glycofullerenes, including new members with 36 mannoses, as compounds able to inhibit a DC-SIGN-dependent cell infection by pseudotyped viral particles. The results obtained in these experiments demonstrate for the first time that these glycoconjugates are adequate to inhibit efficiently an infection process, and therefore, they can be considered as very promising and interesting tools to interfere in biological events where lectins such as DC-SIGN are involved.

Chemoenzymatic Synthesis of O-Mannosylpeptides in Solution and on Solid Phase

Authors: Robert Šardzík, Anthony P. Green, Nicolas Laurent, Peter Both, Carolina Fontana, Josef Voglmeir, Martin J. Weissenborn, Rose Haddoub, Paola Grassi, Stuart M. Haslam, Göran Widmalm, and Sabine L. Flitsch

Journal reference: J. Am. Chem. Soc., 2012, 134 (10), pp 4521–4524
DOI: 10.1021/ja211861m

 

Abstract
O-Mannosyl glycans are known to play an important role in regulating the function of α-dystroglycan (α-DG), as defective glycosylation is associated with various phenotypes of congenital muscular dystrophy. Despite the well-established biological significance of these glycans, questions regarding their precise molecular function remain unanswered. Further biological investigation will require synthetic methods for the generation of pure samples of homogeneous glycopeptides with diverse sequences. Here we describe the first total syntheses of glycopeptides containing the tetrasaccharide NeuNAcα2-3Galβ1-4GlcNAcβ1-2Manα, which is reported to be the most abundant O-mannosyl glycan on α-DG. Our approach is based on biomimetic stepwise assembly from the reducing end and also gives access to the naturally occurring mono-, di-, and trisaccharide substructures. In addition to the total synthesis, we have developed a “one-pot” enzymatic cascade leading to the rapid synthesis of the target tetrasaccharide. Finally, solid-phase synthesis of the desired glycopeptides directly on a gold microarray platform is described.

Virus-like glycodendrinanoparticles displaying quasi-equivalent nested polyvalency upon glycoprotein platforms potently block viral infection

Authors: Renato Ribeiro-Viana, Macarena Sánchez-Navarro, Joanna Luczkowiak, Julia R. Koeppe, Rafael Delgado, Javier Rojo, Benjamin G. Davis.

Journal: Nature Communications 2012 DOI: 10.1038/ncomms2302

 

Abstract Ligand polyvalency is a powerful modulator of protein– receptor interactions. Host–pathogen infection interactions are often mediated by glycan ligand–protein interactions, yet its interrogation with very high copy number ligands has been limited to heterogenous systems. Here we report that through the use of nested layers of multivalency we are able to assemble the most highly valent glycodendrimeric constructs yet seen (bearing up to 1,620 glycans). These constructs are pure and well-defined single entities that at diameters of up to 32nm are capable of mimicking pathogens both in size and in their highly glycosylated surfaces. Through this mimicry these glyco-dendri-protein-nano-particles are capable of blocking (at picomolar concentrations) a model of the infection of T- lymphocytes and human dendritic cells by Ebola virus. The high associated polyvalency effects (B>106, B/N ≈102–103) displayed on an unprecedented surface area by precise clusters suggest a general strategy for modulation of such interactions.