Identification of disialic acid-containing glycoproteins in mouse serum: a novel modification of immunoglobulin light chains, vitronectin, and plasminogen

Abstract

Serum glycoproteins are involved in various biologic activities, such as the removal of exogenous antigens, fibrinolysis, and metal transport. Some of them are also useful markers of inflammation and disease. Although the amount of sialic acid increases following inflammation, little attention has been paid to the presence of linkage-specific epitopes in serum, especially the alpha2,8-linkage. In a previous study, we demonstrated that four components in mouse serum contain alpha2,8-linked disialic acid (diSia), based on immunoreactivity with monoclonal antibody 2-4B, which is specific to N-glycolylneuraminic acid (Neu5Gc)alpha2-->(8Neu5Gc alpha2-->)(n-1), n > or = 2 [Yasukawa et al., (2005) Glycobiology, 15, 827-837]. In this study, we purified three components, 30-, 70-, and 120-kDa gp, and identified them as an immunoglobulin (Ig) light chain, vitronectin, and plasminogen, respectively, using matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy analyses. Modifications of these proteins with alpha2,8-linked diSia were chemically confirmed by fluorometric C7/C9 analyses and mild acid hydrolysates-fluorometric anion-exchange chromatography analyses. We also demonstrated that the IgG, IgM, and IgE light chains are commonly modified with alpha2,8-linked diSia. In addition, both mouse and rat vitronectin contained diSia, and the amount of disialylation in vitronectin dramatically decreased after hepatectomy. These results indicate that a novel diSia modification of serum glycoproteins is biologically important for immunologic events and fibrinolysis.

Polysialic acid governs T-cell development by regulating progenitor access to the thymus

“…Finally, ST8Sia IV self-sialylates to create di-sialic acid with an ␣2,8-linkage, and it is possible that the enzyme generates this disaccharide on other protein substrates as well (35). In fact, similar di-sialic acids were identified on common mouse serum glycoproteins (36). Some of the T-cell developmental defects described herein may be mediated by the absence of these di-sialic acids in ST8Sia IV Ϫ/Ϫ mice.…”

Interaction of Platelet Endothelial Cell Adhesion Molecule (PECAM) with α2,6-Sialylated Glycan Regulates Its Cell Surface Residency and Anti-apoptotic Role

“…In our LC/MS analyses of PECAM glycans, we found a NeuGc-NeuGc linear disialic acid on hybrid-type N-glycans. A linear disialic acid has recently been found in serum glycoproteins, such as plasminogen and vitronectin (46), but its biological property remains to be defined. The aspect of whether this disialic acid is a preferred ligand for PECAM is another interesting project for future studies.…”

Matrix Restructuring During Liver Regeneration is Regulated by Glycosylation of the Matrix Glycoprotein Vitronectin

“…neuraminidase treatment, and only the more acidic component of pI 4.1 reacted with mAb S2-566, which specifically recognizes the Neu5Ac 2,8Neu5Ac 2,3Gal structure (Yasukawa, Z., et al 2006). Fig.…”