Di Carluccio Cristina, Gerpe Amor Tania, Lenza Maria Pia, Masi Alessandro Antonio, Abreu Celeste, Longo Viviana, Albano Francesco, Nieto-Fabregat Ferran, Salvatore Paola, Falco Geppino, Santana-Medero Darielys, Fragai Marco, van Kooyk Yvette, Molinaro Antonio, Valdes-Balbin Yury, Vaněk Ondřej, Verez-Bencomo Vicente, Marchetti Roberta, Chiodo Fabrizio, Silipo Alba
Department of Chemical Sciences, University of Naples Federico II, via Cinthia 4, 80126 Naples, Italy.
Department of Biochemistry, Faculty of Science, Charles University, Hlavova 2030/8, 12800 Prague, Czech Republic.
JACS Au. 2025 Apr 30;5(5):2257-2269. doi: 10.1021/jacsau.5c00214. eCollection 2025 May 26.
Siglecs, sialic-acid-binding immunoglobulin-like lectins, are key immune cell receptors that recognize sialic acid residues on cell surfaces. Pathogens and tumor cells exploit Siglecs to evade immune responses and modulate immunity, contributing significantly to infectious disease and cancer pathogenesis. Siglec-7, primarily expressed on natural killer (NK) cells, functions as an inhibitory receptor, tightly regulating the immune activity. This study investigates the interaction between Siglec-7 and the capsular polysaccharide (CPS) of Neisseria meningitidis serogroup Y (Men-Y), a bacterium whose sialylated CPS is critical for virulence. We demonstrate that Men-Y CPS binds to inhibitory Siglec-7, potentially dampening immune recognition. We employed a multifaceted approach, combining biochemical and biophysical techniques to dissect this interaction. Enzyme-linked immunosorbent assays (ELISAs) and fluorescence titrations quantified the binding specificity and affinity. Ligand- and protein-based nuclear magnetic resonance (NMR) spectroscopy, coupled with computational modeling, provides detailed molecular insights. We highlight the critical influence of the Men-Y CPS conformation and sialic acid presentation on Siglec-7 binding. The specific arrangement of α-2,6-linked sialic acids on the CPS is crucial for Siglec-7 binding, demonstrating the importance of the CPS 3D structure. Preliminary immunological assays using stimulated U937 cells (a promonocytic cell line) further support the immunomodulatory role of Siglec-7 mediated by Men-Y CPS. These results offer valuable insights into the development of targeted therapeutic strategies against bacterial infections.
唾液酸结合免疫球蛋白样凝集素（Siglecs）是识别细胞表面唾液酸残基的关键免疫细胞受体。病原体和肿瘤细胞利用Siglecs逃避免疫反应并调节免疫，这在传染病和癌症发病机制中起着重要作用。Siglec-7主要在自然杀伤（NK）细胞上表达，作为一种抑制性受体，严格调节免疫活性。本研究调查了Siglec-7与Y群脑膜炎奈瑟菌（Men-Y）的荚膜多糖（CPS）之间的相互作用，该细菌的唾液酸化CPS对其毒力至关重要。我们证明Men-Y CPS与抑制性Siglec-7结合，可能会减弱免疫识别。我们采用了多方面的方法，结合生化和生物物理技术来剖析这种相互作用。酶联免疫吸附测定（ELISA）和荧光滴定法定量了结合特异性和亲和力。基于配体和蛋白质的核磁共振（NMR）光谱，结合计算建模，提供了详细的分子见解。我们强调了Men-Y CPS构象和唾液酸呈现对Siglec-7结合的关键影响。CPS上α-2,6连接的唾液酸的特定排列对Siglec-7结合至关重要，证明了CPS三维结构的重要性。使用刺激的U937细胞（一种单核细胞系）进行的初步免疫测定进一步支持了Men-Y CPS介导的Siglec-7的免疫调节作用。这些结果为针对细菌感染的靶向治疗策略的开发提供了有价值的见解。
