Unraveling Sugar Binding Modes to DC-SIGN by Employing Fluorinated Carbohydrates.

J Daniel Martínez,F Javier Cañada,Ana Ardá,Bruno Linclau,Sandra Delgado,Cecilia Romanò,Pablo Valverde,Niels C Reichardt,Jesús Jiménez-Barbero,Stefan Oscarson

doi:10.3390/molecules24122337

Abstract

A fluorine nuclear magnetic resonance (19F-NMR)-based method is employed to assess the binding preferences and interaction details of a library of synthetic fluorinated monosaccharides towards dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN), a lectin of biomedical interest, which is involved in different viral infections, including HIV and Ebola, and is able to recognize a variety of self- and non-self-glycans. The strategy employed allows not only screening of a mixture of compounds, but also obtaining valuable information on the specific sugar–protein interactions. The analysis of the data demonstrates that monosaccharides Fuc, Man, Glc, and Gal are able to bind DC-SIGN, although with decreasing affinity. Moreover, a new binding mode between Man moieties and DC-SIGN, which might have biological implications, is also detected for the first time. The combination of the 19F with standard proton saturation transfer difference (1H-STD-NMR) data, assisted by molecular dynamics (MD) simulations, permits us to successfully define this new binding epitope, where Man coordinates a Ca2+ ion of the lectin carbohydrate recognition domain (CRD) through the axial OH-2 and equatorial OH-3 groups, thus mimicking the Fuc/DC-SIGN binding architecture.

Highlights

Carbohydrates are ubiquitous in nature in different combinations, from single monosaccharides to extremely complex glycoconjugates
We applied a strategy that allows the screening of a library of synthetic fluorinated monosaccharides to study the interactions with the biologically relevant lectin dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN) [9]
It is extensively reported that DC-SIGN is able to bind the HIV-1 envelope glycoprotein, gp 120, which is exploited by the virus to enhance its infectivity of T cells [11,12]

Summary

Introduction

Carbohydrates are ubiquitous in nature in different combinations, from single monosaccharides to extremely complex glycoconjugates. Ligand-based NMR experiments are widely used to study the interactions between carbohydrates and receptors in solution [1,2,3,4]. We applied a strategy that allows the screening of a library of synthetic fluorinated monosaccharides to study the interactions with the biologically relevant lectin dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN) [9]. DC-SIGN is a C-type lectin expressed by dendritic cells [10]. It acts as an adhesion receptor in cell–cell interactions, and plays crucial roles in the DC migration and adaptive immune response initiation [10]. Glycan binding to DC-SIGN occurs through direct coordination with one of the structural Ca2+ ions of the lectin carbohydrate recognition domain (CRD)

Methods

Results

Conclusion