Open AccessGalNAc-Tyrosine Is a Ligand of Plant Lectins, Antibodies, and Human and Murine Macrophage Galactose-Type Lectins
Author(s) -
Ruslan Gibadullin,
David W. Farnsworth,
Joseph J. Barchi,
Jeffrey C. Gildersleeve
Publication year - 2017
Publication title -
acs chemical biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.899
H-Index - 111
eISSN - 1554-8937
pISSN - 1554-8929
DOI - 10.1021/acschembio.7b00471
Subject(s) - epitope , biochemistry , glycan , c type lectin , glycosylation , lectin , monoclonal antibody , glycoconjugate , antibody , glycoprotein , biology , siglec , chemistry , microbiology and biotechnology , immunology
In 2011, a new type of protein O-glycosylation was discovered in which N-acetylgalactosamine is attached to the side chain of tyrosine (GalNAc-Tyr). While present on dozens of proteins, the biological roles of GalNAc-Tyr are unknown. To gain insight into this new type of modification, we synthesized a group of GalNAc-Tyr glycopeptides, constructed microarrays, and evaluated potential recognition of GalNAc-Tyr by a series of glycan-binding proteins. Through a series of >150 microarray experiments, we assessed binding properties of a variety of plant lectins, monoclonal antibodies, and endogenous lectins. VVL, HPA, and SBA were all found to bind tightly to GalNAc-Tyr, and several Tn binding antibodies and blood group A antibodies were found to cross-react with GalNAc-Tyr. Thus, detection of GalNAc-Tyr modified proteins is an important consideration when analyzing results from these reagents. Additionally, we evaluated potential recognition by two mammalian lectins, human (hMGL) and murine (mMGL-2) macrophage galactose type C-type lectins. Both hMGL and mMGL-2 bound tightly to GalNAc-Tyr determinants. The apparent K d values (∼1-40 nM) were on par with some of the best known ligands for MGL, such as the Tn antigen. hMGL also bound the natural beta-amyloid peptide containing a GalNAc-Tyr epitope. STD NMR experiments provided structural insights into the molecular basis of recognition. Finally, GalNAc-Tyr was selectively captured by mMGL-2 positive dendritic cells. These results provide the first evidence that GalNAc-Tyr modified proteins and/or peptides may be ligands for hMGL and mMGL-2 and offer unique structures for the design of MGL targeting agents.