Toshiaki Suguri

Modification of sialic acids by 9-O-acetylation is detected in human leucocytes using the lectin property of influenza C virus

Influenza C virus spike glycoprotein HEF specifically recognizes glycoconjugates containing 9-O-acetyl-N-acetylneuraminic acid. The same protein also contains an esterase activity. Taking advantage of these two properties, influenza C virus was used as a very sensitive probe for the detection of traces of 9-O-acetyl-N-acetylneuraminic acid in human leucocytes. The binding of influenza C virus to leucocyte glycoproteins and gangliosides separated by sodium dodecyl sulphate–polyacrylamide gel electrophoresis and thin-layer chromatography, respectively, was assayed using a chromogenic esterase substrate. In this way, glycoproteins of B-lymphocytes and T-lymphocytes were found to contain 9-O-acetylated sialic acids. Of the various 9-O-acetylated gangliosides detected, one had the characteristics of 9-O-acetylated GD3. The identification of 9-O-acetylated sialic acids on distinct glycoproteins and glycolipids should be helpful in assigning a physiological role to this sugar.

S18.14 Detection ofN-acetyl-9-O-acetylneuraminic acid on human lymphocytes

determined as KDNa2o3Gal/31 ~4Glc/31 ~ 1 ceramide, (KDN)GM3 (1). Following this finding, two minor KDNgangliosides were isolated from ovarian fluid of rainbow trout and their structures were established by chemical degradation, methylation analysis and ~H NMR spectroscopy as (KDN)GD la and (9-O-AcKDN)GDla (2). In addition to these gangliosides, several other minor KDN-gangliosides have been identified. The results of these studies have suggested the general existence of KDN-gangliosides in a wider range of animal tissues and the failure to find them was apparently due to the methodology used. To search for KDN-gangliosides, we have set out to develop sensitive probes and availability of different types of KDNglycoconjugates has enabled us to generate monoclonal antibodies which specifically recognize KDN-glycan epitopes such as KDNa2~3Gal/31 ~ and KDNa2~8KDNa2 ~ sequences (3). With these sensitive probes (mAb.kdn3G and mAb. kdn8kdn), the rapid detection not only of major but also minor KDN-glycoconjugates should be feasible, and low relative molecular mass material extracted by chloroform/ methanol from various animal origins was tested for recognition by mAb.kdn3G and mAb.kdn8kdn. We have indeed preliminary evidence for the presence of mAb.kdn3G-positive antigens in some tissues. Our interest in KDN-gangliosides has been extended to the synthesis of neo-KDN-gangliosides, i.e., potentially useful analogues for the corresponding gangliosides, by transferring the KDN residue(s) from CMP-KDN to a variety of Neu5Acgangliosides and asialo-gangliosides with the aid of the KDNtransferase activities that we recently identified (4). (1) Yu Song, K. Kitajima, S. Inoue and Y. Inoue (1991) J. Biol. Chem., 266, 21929-21935; (2) Yu Song, K. Kitajima, S. Inoue, H. Muto, T. Kasama, S. Handa and Y. Inoue (1993) J. Biol. Chem. submitted; (3)Yu Song, K. Kitajima and Y. Inoue (1993) Glycobiology, 3, in press; (4)T. Terada, Yu Song, T. Angata, S. Kitazume, K. Kitajima, S. Inoue, F .A. Troy and Y. Inoue (1993) In the 12th International Symposium on Glycoconjugates.