Discovery of a new sialic acid binding region that regulates Siglec-7

• Published in: Scientific reports 2020-05, Vol.10 (1), p.8647, Article 8647
• Main Authors: Yamakawa, Nao, Yasuda, Yu, Yoshimura, Atsushi, Goshima, Ami, Crocker, Paul R., Vergoten, Gérard, Nishiura, Yuji, Takahashi, Takashi, Hanashima, Shinya, Matsumoto, Kana, Yamaguchi, Yoshiki, Tanaka, Hiroshi, Kitajima, Ken, Sato, Chihiro
• Format: Article
• Language: English
• Subjects: 101/6; 631/45/221; 631/45/72/1202; 82/80; 96/98; Acids; Amino Acid Sequence; Antigens, Differentiation, Myelomonocytic - metabolism; Binding sites; Binding Sites - genetics; Binding Sites - physiology; Conformation; Dialysis; Equilibrium dialysis; Gangliosides - metabolism; Glycoconjugates; Glycoconjugates - metabolism; Humanities and Social Sciences; Humans; Killer Cells, Natural - immunology; Lectins - metabolism; Life Sciences; Ligands; Molecular Conformation; Molecular Docking Simulation; Monocytes; Monocytes - immunology; multidisciplinary; Mutagenesis, Site-Directed; Natural killer cells; NMR; Nuclear magnetic resonance; Science; Science (multidisciplinary); Sialic Acid Binding Ig-like Lectin 3 - metabolism; Sialic Acids - metabolism; Site-directed mutagenesis
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-64887-4

Siglec-7 is a human CD33-like siglec, and is localised predominantly on human natural killer (NK) cells and monocytes. Siglec-7 is considered to function as an immunoreceptor in a sialic acid-dependent manner. However, the underlying mechanisms linking sialic acid-binding and function remain unknown. Here, to gain new insights into the ligand-binding properties of Siglec-7, we carried out in silico analysis and site-directed mutagenesis, and found a new sialic acid-binding region (site 2 containing R67) in addition to the well-known primary ligand-binding region (site 1 containing R124). This was supported by equilibrium dialysis, STD-NMR experiments, and inhibition analysis of GD3-binding toward Siglec-7 using synthetic sialoglycoconjugates and a comprehensive set of ganglioside-based glycoconjugates. Our results suggest that the two ligand-binding sites are potentially controlled by each other due to the flexible conformation of the C-C′ loop of Siglec-7.