Reduced sialylation status in UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE)-deficient mice

• Published in: Glycoconjugate journal Vol. 24; no. 2-3; pp. 125 - 130
• Main Authors: Gagiannis, Daniel, Orthmann, André, Danßmann, Ilona, Schwarzkopf, Martina, Weidemann, Wenke, Horstkorte, Rüdiger
• Format: Journal Article
• Language: English
• Published: United States New York : Kluwer Academic Publishers-Plenum Publishers 01.04.2007; Springer Nature B.V
• Subjects: (Poly)-Sialic acid; Acids; Animals; Biosynthesis; Cell adhesion & migration; Cell Membrane - metabolism; Cell surface; Enzymes; Female; Glycoconjugates - chemistry; Glycoconjugates - metabolism; Heterozygote; Membranes; Mice; Mice, Inbred C57BL; Mice, Knockout; Multienzyme Complexes - deficiency; Multienzyme Complexes - genetics; Multienzyme Complexes - metabolism; Neural cell adhesion molecule; Neural Cell Adhesion Molecules - chemistry; Neural Cell Adhesion Molecules - metabolism; Proteins; Sialic Acids - chemistry; Sialic Acids - metabolism; Tissue Distribution; transferrin; Transferrin - chemistry; Transferrin - metabolism
• ISSN: 0282-0080; 1573-4986
• DOI: 10.1007/s10719-006-9019-7

Sialic acids are widely expressed as terminal carbohydrates on glycoconjugates of eukaryotic cells. They are involved in a variety of cellular functions, such as cell adhesion or signal recognition. The key enzyme of sialic acid biosynthesis is the bifunctional UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE), which catalyzes the first two steps of sialic acid biosynthesis in the cytosol. Previously, we have shown that inactivation of the GNE by gene targeting causes early embryonic lethality in mice, whereas heterozygous GNE-deficient mice are vital. In this study we compared the amount of membrane-bound sialic acids of wildtype mice with those of heterozygous GNE-deficient mice. For that we quantified membrane-bound sialic acid concentration in various organs of wildtype- and heterozygous GNE-deficient mice. We found an organ-specific reduction of membrane-bound sialic acids in heterozygous GNE-deficient mice. The overall reduction was 25%. Additionally, we analyzed transferrin and polysialylated neural cell adhesion molecule (NCAM) by one- or two-dimensional gel electrophoresis. Transferrin-expression was unchanged in heterozygous GNE-deficient mice; however the isoelectric point of transferrin was shifted towards basic pH, indicating a reduced sialylation. Furthermore, the expression of polysialic acids on NCAM was reduced in GNE-deficient mice.