GLYCOSPHINGOLIPID COMPOSITION OF MURINE NEUROBLASTOMA-CELLS - O-ACETYLESTERASE GENE DOWN-REGULATES THE EXPRESSION OF O-ACETYLATED GD3

We have studied the glycosphingolipid composition in an F-ll neuroblastoma cell line originated from hybridization of a mouse neuroblastoma cell line (N18TG-2) with rat dorsal root ganglion cells. The total lipid-bound glucose of F-ll cells was estimated to be 0.28 mu g/mg of protein and the total lipid-bound sialic acid was 0.82 mu g/mg of protein. The major neutral glycosphingolipids were Gb4 (37% of the total neutral glycosphingolipids), Gb3 (15%), LacCer (21%), and GlcCer(15%). The major gangliosides were found to be GM3 (37% of the total gangliosides), GD3 (27%), O-acetylated GD3 (18%), and GD1a (4%), with trace amounts of GD2. The unusually high concentration of O-acetylated GD3 is consistent with its putative role as a tumor marker. Immunocytochemical localization studies of GD3 and O-acetylated GD3, examined by mouse monoclonal antibodies R24 and D1.1, respectively, revealed that the cell bodies and processes were all positively stained. To elucidate the role of O-acetylated GD3 in tumorigenesis, we transfected F-ll cells with the O-acetylesterase gene from influenza C virus. Compared with the original cell line, the transfected cells showed a dramatic increase in the level of GD3 (150% of that in the control cells) and a significant decrease of the concentration of O-acetylated GD3 (27% of control cells). In addition, the transfected F-ll cells exhibited a morphology different from the parental cells with enlarged cell bodies and elongated neurites. We conclude that alteration of ganglioside composition, particularly the expression of GD3 and O-acetylated GD3, may be associated with the morphological changes observed in this cell line. Furthermore, the study has provided direct evidence that cellular ganglioside expression can be manipulated by transfection of cells with a foreign gene and this approach may represent a powerful means of elucidating the biological and physiological functions of gangliosides.