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Glycans are complex biomolecules that encode rich information and regulate various biological processes, such as fertilization, host‐pathogen binding, and immune recognition, through interactions with glycan‐binding proteins. A key driving force for glycan‐protein recognition is the interaction between the π electron density of aromatic amino acid side chains and polarized C─H groups of the pyranose (termed the CH–π interaction). However, the relatively weak binding affinity between glycans and proteins has hindered the application of glycan detection and imaging. Here, computational modeling and molecular dynamics simulations are employed to design a chemical strategy that enhances the CH–π interaction between glycans and proteins by genetically incorporating electron‐rich tryptophan derivatives into a lectin PhoSL, which specifically recognizes core fucosylated N‐linked glycans. This significantly enhances the binding affinity of PhoSL with the core fucose ligand and enables sensitive detection and imaging of core fucosylated glycans in vitro and in xenograft tumors in mice. Further, the study showed that this strategy is applicable to improve the binding affinity of GafD lectin for N‐acetylglucosamine‐containing glycans. The approach thus provides a general and effective way to manipulate glycan‐protein recognition for glycoscience applications. Computational modeling is employed to identify the critical tryptophan residue on PhoSL for recognizing core fucosylated glycans. The tryptophan residue is replaced with electron‐rich derivatives of tryptophan using the genetic code expansion strategy to enhance CH–π interactions between PhoSL and glycans. The engineered lectin is able to detect and image core‐fucosylated glycans in cells and in mice with high sensitivity.

Oncogenic Kras-activated pancreatic ductal adenocarcinoma (PDAC) cells highly rely on an unconventional glutamine catabolic pathway to sustain cell growth. However, little is known about how this pathway is regulated. Here we demonstrate that Kras mutation induces cellular O-linked β-N-acetylglucosamine (O-GlcNAc), a prevalent form of protein glycosylation. Malate dehydrogenase 1 (MDH1), a key enzyme in the glutamine catabolic pathway, is positively regulated by O-GlcNAcylation on serine 189 (S189). Molecular dynamics simulations suggest that S189 glycosylation on monomeric MDH1 enhances the stability of the substrate-binding pocket and strengthens the substrate interactions by serving as a molecular glue. Depletion of O-GlcNAcylation reduces MDH1 activity, impairs glutamine metabolism, sensitizes PDAC cells to oxidative stress, decreases cell proliferation and inhibits tumor growth in nude mice. Furthermore, O-GlcNAcylation levels of MDH1 are elevated in clinical PDAC samples. Our study reveals that O-GlcNAcylation contributes to pancreatic cancer growth by regulating the metabolic activity of MDH1.Kras activation in pancreatic cancer cells induced O-GlcNAc modification of malate dehydrogenase 1, regulating glutamine metabolism and promoting tumor growth.

Ligand-stimulated epidermal growth factor receptor (EGFR) signaling plays fundamental roles in normal cell physiology, such as cell growth, cell proliferation, and cell survival. Deregulation of EGFR signaling contributes to the development and progression of diseases including cancer. Despite its essential role in biology, the mechanisms by which EGFR signaling is regulated in cells are still poorly understood. Here, we demonstrate that O-linked N-acetylglucosamine (O-GlcNAc) modification serves as an important regulator of EGFR intracellular trafficking and degradation. Mechanistically, O-GlcNAcylation of hepatocyte growth factor regulated tyrosine kinase substrate (HGS), a key protein in EGFR intraluminal sorting pathway, inhibits HGS interaction with signal-transducing adaptor molecule (STAM), thereby impairing the formation of endosomal sorting complex required for transport-0 (ESCRT-0). Moreover, O-GlcNAcylation increases HGS ubiquitination and decreases its protein stability in cells. Consequently, HGS O-GlcNAcylation inhibits EGFR intraluminal sorting and lysosomal degradation, leading to the accumulation of EGFR and prolonged EGFR signaling in cells. Furthermore, HGS glycosylation is demonstrated to promote tumor growth in the xenograft study and chemoresistance in liver carcinoma cells. Thus, our study reveals a role of O-GlcNAcylation in regulating receptor tyrosine kinase endocytic trafficking and signaling.