Efficient Preparation and Bioactivity Evaluation of Glycan-Defined Glycoproteins

Owing to the generation of heterogeneous glycoproteins in cells, it is highly difficult to study glycoprotein-mediated biological events and to develop biomedical agents. Thus, general and efficient methods to prepare homogeneous glycoproteins are in high demand. Herein, we report a general method for the efficient preparation of homogeneous glycoproteins that utilizes a combination of genetic code expansion and chemoselective ligation techniques. In the protocol to produce glycan-defined glycoproteins, an alkyne tag-containing protein, generated by genetic encoding of an alkynylated unnatural amino acid, was quantitatively coupled via click chemistry to versatile azide-appended glycans. The glycoproteins produced by the present strategy were found to recognize mammalian cell-surface lectins and enter the cells through lectin-mediated internalization. Also, cell studies exhibited that the glycoprotein containing multiple mannose-6-phosphate residues enters diseased cells lacking specific lysosomal glycosidases by binding to the cell-surface M6P receptor, and subsequently migrates to lysosomes for efficient degradation of stored glycosphingolipids.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2013-2014

This review is the eighth update of the original article published in 1999 on the application of Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2014. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly- saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2018 Wiley Periodicals, Inc. Mass Spec Rev 37:353-491, 2018.

Probing cell-surface carbohydrate binding proteins with dual-modal glycan-conjugated nanoparticles

Dual-modal fluorescent magnetic glyconanoparticles have been prepared and shown to be powerful in probing lectins displayed on pathogenic and mammalian cell surfaces. Blood group H1- and Le(b)-conjugated nanoparticles were found to bind to BabA displaying Helicobacter pylori, and Le(a)- and Le(b)-modified nanoparticles are both recognized by and internalized into DC-SIGN and SIGN-R1 expressing mammalian cells via lectin-mediated endocytosis. In addition, glyconanoparticles block adhesion of H. pylori to mammalian cells, suggesting that they can serve as inhibitors of infection of host cells by this pathogen. It has been also shown that owing to their magnetic properties, glyconanoparticles are useful tools to enrich lectin expressing cells. The combined results indicate that dual-modal glyconanoparticles are biocompatible and that they can be employed in lectin-associated biological studies and biomedical applications.

Glyco-regioisomerism Effect on Lectin-Binding and Cell-Uptake Pathway of Glycopolymer-Containing Nanoparticles

Sugar regioisomerism (glycosidic linkage on different hydroxyl groups of the same sugar) widely exists in various polysaccharides and glycans with a significant contribution to their biological functions. However, the effects of this regioisomersim in glycopolymers and their self-assembled nanoparticles on such functions were almost not investigated previously. In this paper, this regioisomersim effect is studied for self-assembled nanoparticles NP-1-Gal and NP-6-Gal from triblock copolymers carrying different constitutional isomers of the pendent sugar species (1 and 6 denote the glycosidic linkage from the anomeric position and 6 position of the galactose unit, respectively). NP-1-Gal shows strong binding to lectins of Peanut (Arachis hypogea) agglutinin (PNA) and Erythrina cristagalli agglutinin (ECA), while NP-6-Gal does not. More importantly, they show binding behavior similar to the asialoglycoprotein receptor (ASGPR) but different internalization pathways in the Hep G2 cell after ASGPR-mediated endocytosis; i.e., NP-1-Gal can reach the early endosome, late endosome, as well as lysosome, while NP-6-Gal enters the early endosome only but not the others.