A novel approach to decrease sialic acid expression in cells by a C-3 modified N-acetyl-mannosamine [Membrane Biology]

October 2nd, 2014 by Wratil, P. R., Rigol, S., Solecka, B., Kohla, G., Kannicht, C., Reutter, W., Giannis, A., Nguyen, L. D.

Due to its position at the outermost of glycans, sialic acid is involved in a myriad of physiological and pathophysiological cell functions such as host-pathogen interactions, immune regulation and tumor evasion. Inhibitors of cell surface sialylation could be a useful tool in cancer, immune, antibiotic, or antiviral therapy. In this work, four different C-3 modified N-acetyl-mannosamine analogs were tested as potential inhibitors of cell surface sialylation. Peracetylated 2-acetylamino-2-deoxy-3-O-methyl-D-mannose decreases cell surface sialylation in Jurkat cells in a dose dependent manner up to 80 %, quantified by flow cytometry and by enzyme linked lectin assays. High-performance liquid chromatography experiments revealed that not only the concentration of membrane bound but also of cytosolic sialic acid is reduced in treated cells. We have strong evidence that the observed reduction of sialic acid expression in cells is caused by the inhibition of the bifunctional enzyme UDP-GlcNAc-2-epimerase/ManNAc-kinase (GNE/MNK). 2-Acetylamino-2-deoxy-3-O-methyl-D-mannose inhibits the human ManNAc-kinase domain of the GNE/MNK. Binding kinetics of the inhibitor and MNK were evaluated using surface plasmon resonance. Specificity studies with human N-acetyl-glucosamine kinase and hexokinase IV indicated a high specificity of 2-acetylamino-2-deoxy-3-O-methyl-D-mannose for MNK. This substance represents a novel class of inhibitors of sialic acid expression in cells, targeting the key enzyme of sialic acid de novo biosynthesis.