Human Milk Oligosaccharide 2′-Fucosyllactose Inhibits Ligand Binding to C-Type Lectin DC-SIGN but Not to Langerin
Human milk oligosaccharides (HMOs) and their most abundant component, 2′-Fucosyllactose (2′-FL), are known to be immunomodulatory. Previously, it was shown that HMOs and 2′-FL bind to the C-type lectin receptor DC-SIGN. Here we show, using a ligand-receptor competition assay, that a whole mixture of...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2022-11-01
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| Series: | International Journal of Molecular Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1422-0067/23/23/14745 |
| Summary: | Human milk oligosaccharides (HMOs) and their most abundant component, 2′-Fucosyllactose (2′-FL), are known to be immunomodulatory. Previously, it was shown that HMOs and 2′-FL bind to the C-type lectin receptor DC-SIGN. Here we show, using a ligand-receptor competition assay, that a whole mixture of HMOs from pooled human milk (HMOS) and 2′-FL inhibit the binding of the carbohydrate-binding receptor DC-SIGN to its prototypical ligands, fucose and the oligosaccharide Lewis-B, (Le<sup>b</sup>) in a dose-dependent way. Interestingly, such inhibition by HMOS and 2′-FL was not detected for another C-type lectin, langerin, which is evolutionarily similar to DC-SIGN. The cell-ligand competition assay using DC-SIGN expressing cells confirmed that 2′-FL inhibits the binding of DC-SIGN to Le<sup>b</sup>. Molecular dynamic (MD) simulations show that 2′-FL exists in a preorganized bioactive conformation before binding to DC-SIGN and this conformation is retained after binding to DC-SIGN. Le<sup>b</sup> has more flexible conformations and utilizes two binding modes, which operate one at a time via its two fucoses to bind to DC-SIGN. Our hypothesis is that 2′-FL may have a reduced entropic penalty due to its preorganized state, compared to Le<sup>b</sup>, and it has a lower binding enthalpy, suggesting a better binding to DC-SIGN. Thus, due to the better binding to DC-SIGN, 2′-FL may replace Le<sup>b</sup> from its binding pocket in DC-SIGN. The MD simulations also showed that 2′-FL does not bind to langerin. Our studies confirm 2′-FL as a specific ligand for DC-SIGN and suggest that 2′-FL can replace other DC-SIGN ligands from its binding pocket during the ligand-receptor interactions in possible immunomodulatory processes. |
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| ISSN: | 1661-6596 1422-0067 |