Structure-based rationale for differential recognition of lacto- and neolacto- series glycosphingolipids by the N-terminal domain of human galectin-8

Abstract

Glycosphingolipids are ubiquitous cell surface molecules undertaking fundamental cellular processes. Lacto-N-tetraose (LNT) and lacto-N-neotetraose (LNnT) are the representative core structures for lacto- and neolacto-series glycosphingolipids. These glycolipids are the carriers to the blood group antigen and human natural killer antigens mainly found on blood cells, and are also principal components in human milk, contributing to infant health. The β-galactoside recognising galectins mediate various cellular functions of these glycosphingolipids. We report crystallographic structures of the galectin-8 N-terminal domain (galectin-8N) in complex with LNT and LNnT. We reveal the first example in which the non-reducing end of LNT binds to the primary binding site of a galectin, and provide a structure-based rationale for the significant ten-fold difference in binding affinities of galectin-8N toward LNT compared to LNnT, such a magnitude of difference not being observed for any other galectin. In addition, the LNnT complex showed that the unique Arg59 has ability to adopt a new orientation, and comparison of glycerol- and lactose-bound galectin-8N structures reveals a minimum atomic framework for ligand recognition. Overall, these results enhance our understanding of glycosphingolipids interactions with galectin-8N, and highlight a structure-based rationale for its significantly different affinity for components of biologically relevant glycosphingolipids.

Breast milk-derived human milk oligosaccharides promote Bifidobacterium interactions within a single ecosystem

“…Overall fewer isolates appeared to utilise LNnT, likely because LNnT is a structurally more complex HMO that contains a glycosidic linkage within the nonreducing terminal disaccharide, Galβ1-3/4GlcNAc [44]. LH11 from infant V1 grew in the presence of LNnT; however, the metabolic by-products did not support growth of any other identified strains in this infant.…”

Altered Gut Microbiota is Involved in the Anti‐Hypertensive Effects of Vitamin C in Spontaneously Hypertensive Rat

“…These types of glycosphingolipids carry the functional antigens such as HNK‐1 and are critically involved in the immune system. [ 35,36 ] Over‐activated synthesis of the lacto and neolacto series of glycosphingolipid may cause inflammation and the treatment of VC significantly decreased the number of OTUs associated with this function (Figure 4C) and decrease the inflammatory responses in the intestine (Figure 6D–F). Functional analysis of the gut microbiota also suggested increase of the OTUs related to Alzheimer's disease in SHR‐Veh comparing to WKY‐Veh, and low dosage of VC was able to reduce it (Figure 4D).…”

Conformations of the type-1 lacto-N-biose I unit in protein complex structures

“…These distributions were explained by steric hindrance with the O4 hydroxyl. The rare tg conformer of GlcNAc in human galectin-8 is stabilized by a hydrogen bond to Glu89 (Bohari et al, 2016), whereas that in type-1 A antigen bound to the norovirus P domain is not supported by any protein interactions and the electron density is relatively ambiguous in this region (Kubota et al, 2012). The rare tg conformer of the Gal in -LNB bound to the GH136 LNBase is stabilized by the shape complementarity of surrounding hydrophobic residues (Yamada et al, 2017).…”

“…The PDB contains LNB or LNT structures bound to human galectins (galectin-1, galectin-3, galectin-4, galectin-7 and galectin-8) as a part of a lacto-series of glycosphingolipids. The LNB unit of LNT bound to the N-terminal domain of the galectin-8 structure was clearly visible (PDB entry 5t7t), probably because its nonreducing-end -Gal residue exhibits extensive hydrogen-bonding interactions with the protein (Bohari et al, 2016). LNT was modelled in the crystal structure of galectin-3 determined at 1.55 Å resolution (PDB entry 4lbm; Fig.…”