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Siglec-6 mediates the uptake of extracellular vesicles through a noncanonical glycolipid binding pocket.

Edward N SchmidtDimitra LamprinakiKelli A McCordMaju JoeMirat SojitraAyk WaldowJasmine NguyenJohn MonyrorElena N KitovaFahima MozanehXue Yan GuoJaesoo JungJhon R EnterinaGour C DaskhanLing HanAmanda R KryslerChristopher R CromwellBasil P HubbardLori J WestMarianna KulkaSimonetta SipioneJohn S KlassenRatmir DerdaTodd L LowaryLara K MahalMeghan R RiddellMatthew Scott Macauley
Published in: Nature communications (2023)
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.
Keyphrases
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