Tetanus toxin interaction with human erythrocytes. I. Properties of polysialoganglioside association with the cell surface

Human erythrocytes in suspension acquire gangliosides containing di- and trisialosyl residues added to the maintenance medium. This is reflected in the increased cell-associated sialic acid content and ability to bind ¹²⁵I-labeled tetanus toxin. A salt-sensitive and a salt-insensitive ganglioside-mediated toxin-cell surface association is detected which is reduced after sialidase treatment of ganglioside-supplemented cells. The salt-insensitive ganglioside-cell association is saturable after 2 h incubation in 0.3 M mannitol buffer and has an optimum at pH 5. The association process is higher at 37°C than at 4°C, depends on cell density, and is considerably higher in metabolically active cells compared to lysed cells. Pretreatment of cells with trypsin decreases the salt-resistant toxin association with ganglioside-supplemented cells. In contrast, glutaraldehyde-fixed cells treated with trypsin and supplemented with gangliosides bind more toxin which is insensitive to salt. Ganglioside-mediated tetanus toxin binding to the intact erythrocyte membrane can be utilized as a model system for studying the role of glycolipids in membrane function.