Rational-Differential Design of Highly Specific Glycomimetic Ligands: Targeting DC-SIGN and Excluding Langerin Recognition

Abstract

At the surface of dendritic cells, C-type lectin receptors (CLRs) allow the recognition of carbohydrate-based PAMPS or DAMPS (pathogen- or danger-associated molecular patterns, respectively) and promote immune response regulation. However, some CLRs are hijacked by viral and bacterial pathogens. Thus, the design of ligands able to target specifically one CLR, to either modulate an immune response or to inhibit a given infection mechanism, has great potential value in therapeutic design. A case study is the selective blocking of DC-SIGN, involved notably in HIV trans-infection of T lymphocytes, without interfering with langerin-mediated HIV clearance. This is a challenging task due to their overlapping carbohydrate specificity. Toward the rational design of DC-SIGN selective ligands, we performed a comparative affinity study between DC-SIGN and langerin with natural ligands. We found that GlcNAc is recognized by both CLRs; however, selective sulfation are shown to increase the selectivity in favor of langerin. With the combination of site-directed mutagenesis and X-ray structural analysis of the langerin/GlcNS6S complex, we highlighted that 6-sulfation of the carbohydrate ligand induced langerin specificity. Additionally, the K313 residue from langerin was identified as a critical feature of its binding site. Using a rational and a differential approach in the study of CLR binding sites, we designed, synthesized, and characterized a new glycomimetic, which is highly specific for DC-SIGN vs langerin. STD NMR, SPR, and ITC characterizations show that compound 7 conserved the overall binding mode of the natural disaccharide while possessing an improved affinity and a strict specificity for DC-SIGN.

Enhancing Potency and Selectivity of a DC‐SIGN Glycomimetic Ligand by Fragment‐Based Design: Structural Basis

“…These structurala djustments for the p-hydroxymethylenebenzylamide arm illustratet he plasticityo ft he CRD backboneo fD C-SIGN as previously observed for langerin. [13] In the crystal, 16 interacts similarly to the previously characterizedb inding mode fort he glycomimetics 1-3 [3,14] exploiting Val351 side chain for nonpolari nteractions with the cyclohexane ring. Here, for the first time, details of the interaction of the benzylamide arm with the primary CRD surface, previously suggested by NMR studies, are highlighted.…”

“…[2] Mosti mportantly,t hese structuralm odificationsa lso led to improved selectivity against the related C-type lectin langerin, which could be explained by comparatives tructural analysiso ft he two proteins. [3] In this work, we describe our efforts to improvet he affinity of the pseudo-dimannoside ligandsb yc omputationald esign, using af ragment-based screeningi nt he X-ray structure of DC-SIGN carbohydrate recognition domain (CRD) in complex with 1 (PDB 2XR5; PDB = Protein Data Bank). Thiss creening identified several moieties, predicted to bind to sites adjacent to the boundp seudo-dimannoside, and potentially amenable to modify its structures.…”

On‐Chip Screening of a Glycomimetic Library with C‐Type Lectins Reveals Structural Features Responsible for Preferential Binding of Dectin‐2 over DC‐SIGN/R and Langerin

“…DC‐SIGN exhibits a good recognition of many fucose‐based Lewis‐type ligands (Le x , Le a , Le b , and Le y ), as well as of the A, B, and H blood group antigens.Langerin binds with good affinity only the blood group antigens B and A, whereas Le a , Le b , Le y , and Le x are poorly recognized . Moreover, opposite to DC‐SIGN, langerin selectively recognizes sulfated Gal, GalNac, and glycosaminoglycans . Additionally, a divergent structural organization and their distinct expression locations suggest fundamentally different biological roles for these two CLRs.…”

“…When used in multivalent constructs, they were found to block DC‐SIGN‐mediated infection with activities up to the nanomolar level both in HIV and Ebola infection models . Notably, the bisbenzylamide derivatives 6 a and 6 b also exhibited strong selectivity towards DC‐SIGN and did not bind to langerin, a CLR that shares with DC‐SIGN a similar set of ligands but, rather than spreading the infection, facilitates HIV eradication …”

Design and synthesis of glycomimetics: Recent advances

“…A further elaboration of the pseudodisaccharide 28 , the 6‐amino derivative 32 , was recently designed to select for DC‐SIGN and against Langerin, a mannose‐binding C‐lectin of Langerhan cells that binds to HIV envelope glycoprotein gp120 with protective effects. The design of 32 was based on comparative analysis of the two lectin structures in the vicinity of the sugar‐binding sites, which revealed the presence and functional significance of a lysine residue in Langerin (Lys313), which is absent in DC‐SIGN.…”