Lectin affinity chromatography of articular cartilage fibromodulin: Some molecules have keratan sulphate chains exclusively capped by α(2-3)-linked sialic acid

Abstract

Fibromodulin from bovine articular cartilage has been subjected to lectin affinity chromatography by Sambucus nigra lectin which binds α(2-6)- linked N-acetylneuraminic acid, and the structure of the keratan sulphate in the binding and non-binding fractions examined by keratanase II digestion and subsequent high pH anion exchange chromatography. It has been confirmed that the keratan sulphate chains attached to fibromodulin isolated from bovine articular cartilage may have the chain terminating N-acetylneuraminic acid residue α(2-3)- or α(2-6)-linked to the adjacent galactose residue. Although the abundance of α(2-6)-linked N-acetylneuraminic acid (ca. 22%) is such that this could cap one of the four chains in almost all fibromodulin molecules, it was found that ca. 34% of the fibromodulin proteoglycan molecules from bovine articular cartilage were capped exclusively with α(2-3)-linked N-acetylneuraminic acid. The remainder of the fibromodulin proteoglycans, which bound to the lectin had a mixture of α(2-3)- and α(2-6)-linked N-acetylneuraminic acid capping structures. The keratan sulphates attached to fibromodulin molecules capped exclusively with α(2-3)- linked N-acetylneuraminic acid were found to have a higher level of galactose sulphation than those from fibromodulin with both α(2-3)- and α(2-6)-linked N-acetylneuraminic acid caps, which bound to the Sambucus nigra lectin. In addition, both pools contained chains of similar length (ca. 8-9 disaccharides). Both also contained α(1-3)-linked fucose, showing that this feature does not co-distribute with α(2-6)-linked N-acetylneuraminic acid, although these two features are present only in mature articular cartilage. These data show that there are discrete populations of fibromodulin within articular cartilage, which may have differing impacts upon tissue processes.

Galactose 6-O-Sulfotransferases Are Not Required for the Generation of Siglec-F Ligands in Leukocytes or Lung Tissue

“…Because these structures can be capped with sialic acid (62), they have the potential to serve as Siglec-F ligands. However, analysis of such chains was not achievable by our mass spectrometry methods.…”

Unique glycosignature for intervertebral disc and articular cartilage cells and tissues in immaturity and maturity

“…Cellular fibronectin contains both α-(1→6)-linked Fuc and ⌏-(2→3)-linked sialylation. The fibronectin glycosylation varies depending on tissue and cell types and with pathological conditions such as rheumatoid arthritis 40 . α-(1→6)-linked Fuc, already reported on primary chondrocytes 41 , was observed exclusively on chondrocytes in this study ( Figs 1 and 2 ) which suggests a cartilage-specific tropism for this structure on these cells 28 , potentially related to a role in tissue organisation.…”

“…This protein has a role in structural maintenance of collagen fibrils, with KS controlling collagen fibril diameter and interfibrillar spacing. Bovine KS is modified with sulfated Gal and GlcNAc, α-(2→3)- and α-(2→6)-linked sialic acid and α-(1→3)-linked fucose, the latter two structures only appearing upon maturity ( Figs 1 and 2 ) 40 . Similar trends were observed in this study, with an increase in α-(2→6)-sialic acid in mature cartilage ECM combined with a decrease in α-(2→3)-linked sialylation while the inverse was observed for α-(2→6)-sialylation in NP and AF ECM, which may be related to tissue organisation and remodelling over development.…”

Proteoglycan form and function: A comprehensive nomenclature of proteoglycans

“…Indeed, this domain, as that of osteoadherin (see below), physically interacts with basic clusters of several heparin-binding growth factors and cytokines [ 468 ]. Fibromodulin is a major KSPG [ 469 ] and some molecules contain KS chains exclusively capped with α(2–3)-linked sialic acid [ 470 ]. It regulates collagen fibrillogenesis during corneal development [ 471 ].…”