Institution: | 1. Department of Chemical Sciences, University of Naples Federico II, Via Cintia 4, 80126 Napoli, Italy
These authors contributed equally to this work.;2. Department of Chemistry “Ugo Schiff”, University of Florence, Polo Scientifico e Tecnologico, 50019 Sesto Fiorentino, Firenze, Italy
These authors contributed equally to this work.;3. Dipartimento di Chimica, Università degli Studi di Milano, Via C. Golgi, 19, 20133 Milano, Italy;4. Department of Biochemistry, Faculty of Science, Charles University, Hlavova 2030/8, 12800 Prague, Czech Republic;5. Department of Chemistry “Ugo Schiff”, University of Florence, Polo Scientifico e Tecnologico, 50019 Sesto Fiorentino, Firenze, Italy;6. Department of Chemical Sciences, University of Naples Federico II, Via Cintia 4, 80126 Napoli, Italy
Department of Chemistry, School of Science, Osaka University, Osaka University Machikaneyama, Toyonaka, Osaka, 560-0043 Japan;7. Department of Chemical Sciences, University of Naples Federico II, Via Cintia 4, 80126 Napoli, Italy |
Abstract: | We investigated two recently synthesized and characterized sialyl derivatives, bearing the Neu5Ac-α-(2-6)-Gal epitope, as promising binders for Siglec-7, an inhibitory Siglec mainly found on natural killer cells. A variety of sialoglycan structures can be recognized by Siglec-7 with implications in the modulation of immune responses. Notably, overexpression of sialylated glycans recognized by Siglec-7 can be associated with the progression of several tumors, including melanoma and renal cell carcinoma. NOE-based NMR techniques, including Saturation Transfer Difference and transferred-NOESY NMR, together with molecular docking and dynamic simulations were combined to shed light on the molecular basis of Siglec-7 recognition of two conformationally constrained Sialyl-Tn antigen analogs. We, therefore, identify the ligands epitope mapping and their conformational features and propose 3D models accurately describing the protein-ligand complexes. We found that the binding site of Siglec-7 can accommodate both synthetic analogs, with the sialic acid mainly involved in the interaction. Moreover, the flexibility of Siglec-7 loops allows a preferred accommodation of the more rigid compound bearing a biphenyl moiety at position 9 of the sialic acid that contributed to the interaction to a large extent. Our findings provided insights for developing potential novel high affinity ligands for Siglec-7 to hinder tumor evasion. |