Unveiling Molecular Recognition of Sialoglycans by Human Siglec-10

Rosa Ester Forgione,C Di Carluccio,Juan Guzmán-Caldentey,Pompea Del Vecchio,Yoshiyuki Manabe,Sonsoles Martín-Santamaría,Filomena Battista,Angela Arciello,Rosa Gaglione,Alba Silipo,Koichi Fukase,Paul R Crocker Crocker,Antonio Molinaro,Fabrizio Chiodo,Roberta Marchetti

doi:10.2139/ssrn.3587003

Abstract

Siglec-10 is an inhibitory I-type lectin, selectively recognizing sialoglycans exposed on cell surfaces, involved in several patho-physiological processes. The key role Siglec-10 plays in the regulation of immune cell functions has made it a potential target for the development of immunotherapeutics against a broad range of diseases. Though, a detailed understanding of sialoglycans recognition by Siglec-10 is still an unmet challenge; neither the crystal structure of the protein nor the atomic description of its interactions with complex glycans had been indeed previously described.We present here the first insights of the molecular mechanisms regulating the interaction between Siglec-10 and naturally occurring sialoglycans. We used combined spectroscopic, computational and biophysical approaches to dissect glycans’ interactome and conformation upon binding, and to afford a description of the 3D complexes. Our outcomes provide a privileged structural perspective for the rational design and development of novel high affinity ligands to control the receptor functionality.

Highlights

Siglecs constitute a family of cell surface immunomodulatory receptors belonging to the immunoglobulin (Ig) superfamily that act as critical regulators of immune system (Crocker et al, 2007; Duan and Paulson, 2020; Macauley et al, 2014; Laubli and Varki, 2019) through the specific recognition of sialic acids, hallmarks of vertebrate self-glycans
In summary, the interaction of Siglec-10 with differently sialylated glycans was here investigated by an integrated approach based on NMR, docking, and molecular modeling
A comparison of the epitope maps obtained for a2,3- and a2,6-sialoglycans, which constitute the terminal end of the canonical sialylated complex-type N-glycans exposed on mammalian cells, highlighted that in each case the binding process to Siglec-10 was mainly driven by the sialic acid moiety, giving a 100% STDepitope fit, and galactose unit, whereas the N-acetylglucosamine pointed away from Siglec-10 binding pocket

Summary

Introduction

Siglecs (sialic acid-binding immunoglobulin-like lectins) constitute a family of cell surface immunomodulatory receptors belonging to the immunoglobulin (Ig) superfamily that act as critical regulators of immune system (Crocker et al, 2007; Duan and Paulson, 2020; Macauley et al, 2014; Laubli and Varki, 2019) through the specific recognition of sialic acids, hallmarks of vertebrate self-glycans. Feared human pathogens evolved the ability to shield their envelope glycans with sialic acid, mimicking Self Associated Molecular Patterns (Liu et al, 2017; Chang and Nizet, 2014) and exploiting the interaction with inhibitory Siglecs to escape host immune surveillance. In this context, the Siglec-sialoglycan axis is, an emerging attractive therapeutic target to prevent or affect the course of several immune (cancer, autoimmune, and infectious) diseases. These single-pass transmembrane proteins possess an extracellular N-terminal V-set domain, involved in the recognition of specific sialoglycans, and most of them encompass, in their cytoplasmic tails, one or more immunoreceptor tyrosine-based inhibitory motifs (ITIMs), involved in negative intracellular signaling pathways (Crocker et al, 2007; Duan and Paulson, 2020; Macauley et al, 2014)

Methods

Results

Conclusion