Immunomodulatory Siglecs are controlled by their glycoprotein and glycolipid ligands. Siglec-glycolipid interactions are often studied outside the context of a lipid bilayer, missing the complex behaviors of glycolipids in a membrane. Through optimizing a liposomal formulation to dissect Siglec–glycolipid interactions, it is shown that Siglec-6 can recognize glycolipids independent of its canonical binding pocket, suggesting that Siglec-6 possesses a secondary binding pocket tailored for recognizing glycolipids in a bilayer. A panel of synthetic neoglycolipids is used to probe the specificity of this glycolipid binding pocket on Siglec-6, leading to the development of a neoglycolipid with higher avidity for Siglec-6 compared to natural glycolipids. This neoglycolipid facilitates the delivery of liposomes to Siglec-6 on human mast cells, memory B-cells and placental syncytiotrophoblasts. A physiological relevance for glycolipid recognition by Siglec-6 is revealed for the binding and internalization of extracellular vesicles. These results demonstrate a unique and physiologically relevant ability of Siglec-6 to recognize glycolipids in a membrane.

免疫调节 Siglec 受其糖蛋白和糖脂配体控制。Siglec-糖脂相互作用通常在脂质双层的背景之外进行研究，而忽略了膜中糖脂的复杂行为。通过优化脂质体制剂来剖析 Siglec-糖脂相互作用，表明 Siglec-6 可以独立于其经典结合口袋识别糖脂，这表明 Siglec-6 具有一个为识别双层中的糖脂而量身定制的二级结合口袋。一组合成的新糖脂用于探测该糖脂结合口袋对 Siglec-6 的特异性，导致与天然糖脂相比，开发出对 Siglec-6 具有更高亲和力的新糖脂。这种新糖脂有助于将脂质体递送至人肥大细胞、记忆 B 细胞和胎盘合体滋养层细胞上的 Siglec-6。揭示了 Siglec-6 识别糖脂的生理相关性与细胞外囊泡的结合和内化。这些结果表明 Siglec-6 具有识别膜中糖脂的独特且生理相关能力。