Recognition roles of the carbohydrate glycotopes of human and bovine lactoferrins in lectin-N-glycan interactions

A biotechnological tool for glycoprotein desialylation based on immobilized neuraminidase from Clostridium perfringens

Background

Sialic acids are widely distributed in nature and have biological relevance owing to their varied structural and functional roles. Immobilized neuraminidase can selectively remove terminal N-acetyl neuraminic acid from glycoproteins without altering the protein backbone while it can be easily removed from the reaction mixture avoiding sample contamination. This enables the evaluation of changes in glycoprotein performance upon desialylation.

Methods

Neuraminidase was immobilized onto agarose activated with cyanate ester groups and further used for desialylation of model glycoproteins, a lysate from tumour cells and tumour cells. Desialylation process was analysed by lectin binding assay, determination of sialyl-Tn or flow cytometry.

Results

Clostridium perfringens neuraminidase was immobilized with 91 % yield and expressed activity yield was of 41%. It was effective in the desialylation of bovine fetal serum fetuin, bovine lactoferrin and ovine submaxilar mucin. A decrease in sialic-specific SNA lectin recognition of 83% and 53 % was observed for fetuin and lactoferrin with a concomitant increase in galactose specific ECA and PNA lectin recognition. Likewise, a decrease in the recognition of a specific antibody (82%) upon mucin desialylation was observed. Moreover, desialylation of a protein lysate from the sialic acid-rich cell line TA3/Ha was also possible leading to a decrease in 47 % in SNA recognition. Immobilized neuraminidase kept 100% of its initial activity upon five desialylation cycles.

Conclusions

Immobilized neuraminidase is an interesting as well as a robust biotechnological tool for enzymatic desialylation purposes.

General significance

Immobilized neuraminidase would contribute to understand the role of sialic acid in biological processes.

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Neuraminidase immobilization was successfully achieved.

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Immobilized neuraminidase was effective in the desialylation of several model glycoproteins.

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TA3/Ha tumour cell lysates were desialylated with immobilized neuraminidase.

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Immobilized neuraminidase was successfully re-used.

Dietary N-Glycans from Bovine Lactoferrin and TLR Modulation

SCOPE

Bovine lactoferrin (bLF) is an ingredient of food supplements and infant formulas given its antimicrobial and antiviral properties. We modified bLF enzymatically to alter its N-glycosylation and to isolate the glycan chains. The aims of this study include (1) to evaluate whether such derivates induce responses via pattern recognition receptors namely Toll-like receptors (TLRs) and (2) to relate those responses to their different glycosylation profiles.

METHODS AND RESULTS

The unmodified and modified bLF fractions are incubated with reporter cell lines expressing pattern recognition receptors. Afterwards, we screen for TLRs and analyze for nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB) activation. Activation of reporter cell lines show that signaling is highly dependent on TLRs. The activation pattern of bLF is reduced with the desialylated form and increased with the demannosylated form. In reporter cells for TLR, bLF activate TLR-4 and inhibit TLR-3. The isolated glycans from bLF inhibit TLR-8. TLR-2, TLR-5, TLR-7, and TLR-9 are not significantly altered.

CONCLUSION

The profile of glycosylation is key for the biological activity of bLF. By understanding how this affects the human defense responses, the bLF glycan profile can be modified to enhance its immunomodulatory effects when used as a dietary ingredient.

Profiling temporal changes in bovine milk lactoferrin glycosylation using lectin microarrays

The bovine milk glycoprotein bovine lactoferrin (bLF) has a variety of biological activities related to its constituent glycans. However, little is known about bLF's oligosaccharide structural changes over the course of lactation. BLF was isolated at 13 time points during the first three months of lactation from three individual cows and glycosylation changes were profiled by lectin microarrays. Substantial profile differences between early and late lactation were observed and accompanying monosaccharide analysis revealed that the occurrence of the non-human sialic acid, N-glycolylneuraminic acid, was greater during early stage milk production. Overall, the data suggested that more diverse complex-type oligosaccharide structures were present on bLF during early lactation with an abundance of oligomannose type glycans in later lactation. The differences in the glycoprofiles of bLF from colostrum to mature milk suggest that these may have different functionality in vivo.