Glycomics by ion mobility tandem mass spectrometry of chondroitin sulfate disaccharide domain in biglycan

Biglycan (BGN), a small leucine-rich repeat proteoglycan, is involved in a variety of pathological processes including malignant transformation, for which the upregulation of BGN was found related to cancer cell invasiveness. Because the functions of BGN are mediated by its chondroitin/dermatan sulfate (CS/DS) chains through the sulfates, the determination of CS/DS structure and sulfation pattern is of major importance. In this study, we have implemented an advanced glycomics method based on ion mobility separation (IMS) mass spectrometry (MS) and tandem MS (MS/MS) to characterize the CS disaccharide domains in BGN. The high separation efficiency and sensitivity of this technique allowed the discrimination of five distinct CS disaccharide motifs, of which four irregulated in their sulfation pattern. For the first time, trisulfated unsaturated and bisulfated saturated disaccharides were found in BGN, the latter species documenting the non-reducing end of the chains. The structural investigation by IMS MS/MS disclosed that in one or both of the CS/DS chains, the non-reducing end is 3-O-sulfated GlcA in a rather rare bisulfated motif having the structure 3-O-sulfated GlcA-4-O-sulfated GalNAc. Considering the role played by BGN in cancer cell spreading, the influence on this process of the newly identified sequences will be investigated in the future.

Automated summary

In this study, an advanced glycomics method based on ion mobility separation mass spectrometry and tandem mass spectrometry was used to characterize the chondroitin sulfate disaccharide domains in BGN. Five distinct disaccharide motifs were identified in BGN, with four showing irregular sulfation patterns. Trisulfated unsaturated and bisulfated saturated disaccharides were found, the latter indicating the non-reducing end of the chains. Structural investigation revealed a rare bisulfated motif, 3-O-sulfated GlcA-4-O-sulfated GalNAc, at the non-reducing end of one or both CS/DS chains in BGN. The influence of these newly identified sequences on cancer cell spreading will be investigated in future studies.