Lectin receptors and cell surface recognition.

Ricin-resistant (RicR) baby hamster kidney (BHK) cell lines have been classified into a small group (3 lines) showing a minimal surface change from wild type and a larger group (20 lines) which exhibit more extreme alterations in surface properties. Glycopeptides released by pronase from some RicR lines in the second group show a lower content of sialic acid, galactose, and N-acetylglucosamine and greatly reduced binding activity for ricin. Treatment of receptor deficient glycopeptides or RicR cells with neuraminidase reveals new ricin receptors and renders the cells very sensitive to ricin. Several classes of ricin receptors are postulated for BHK cells, some of which are cryptic and under independent genetic control from receptors selected against with ricin. The cell lines showing greatly altered surface properties in general adhere poorly to a substratum and also aggregate poorly compared to wild type or RicR cells showing minimal surface change. The lactoperoxidase iodinateable 250K glycoprotein of normal BHK cells is lacking in all but one of these RicR cell lines. The role of 250K glycoprotein in normal cell adhesion is considered and a hypothesis proposed relating changes in surface organization of the 250K glycoprotein to alterations in receptors induced by ricin selection.