A Computational and Chemical Design Strategy for Manipulating Glycan-Protein Recognition

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.

Establishment of a novel lectin-antibody ELISA system to determine core-fucosylated haptoglobin

BACKGROUND

Fucosylated haptoglobin (Fuc-Hpt) is a novel cancer biomarker that increases in various pathological conditions. We previously established a Fuc-Hpt lectin-antibody assay using Aleuria aurantia lectin (AAL), and applied this to diagnose several diseases, including various cancers. AAL recognizes both α1-3/1-4 and α1-6 fucosylation on N/O-linked glycans. These fucosylation types differ in biological function, and in regulation by different fucosyltransferases. Recently, we identified a novel lectin, Pholiota squarrosa lectin (PhoSL), which specifically recognizes α1-6 fucosylation (core-fucosylation).

METHODS

We developed a lectin-antibody ELISA kit using PhoSL to determine core-Fuc-Hpt levels in sera from colorectal or pancreatic cancer patients.

RESULTS

Serum levels of AAL-reactive Hpt are higher in pancreatic cancer patients, whereas those of PhoSL-reactive Hpt are higher in colorectal cancer patients. Mass spectrometry analyses of Hpt fucosylation levels were consistent with lectin-antibody ELISA results. Hpt-transfected colorectal cancer cell lines produced significant amounts of core-Fuc-Hpt, suggesting that colorectal cancer tissues produce core-Fuc-Hpt.

CONCLUSIONS

These differences in Fuc-Hpt patterns might depend on cancer cells and the surrounding cells, which produce Hpt.