THE EXPRESSION OF CARBOHYDRATE BLOOD-GROUP ANTIGENS CORRELATES WITH HEAT-RESISTANCE

Recent data indicate that cells may resist heat shock via more than on e route: heat shock protein synthesis and other still ill-defined mech anisms. We investigated this phenomenon using four types of cells deri ved from a single rat colon carcinoma: clones REGb and PROb; PRO A(+), a glycosylation variant of PROb selected for its high expression of b lood group A antigen; and Phs, a thermoresistant variant of PROb selec ted by repeated sublethal heat treatments. Basal heat resistance was c learly associated with the level of cell surface expression of blood g roup H and A antigens. Biosynthesis of these carbohydrate structures r equires two glycosyltransferases, H and A enzymes, whose activities ar e also correlated with basal heat resistance. In addition, heat sensit ive REGb cells were rendered more resistant by transfection with the g ene encoding for H enzyme, allowing expression of H antigen. Thus, the se terminal glycosylations could play a role as cellular protectors ag ainst heat treatment. Blood group carbohydrate antigens were mainly lo cated on O-linked carbohydrate chains of a major glycoprotein of 200 k Da and to a lesser extent on N-linked chains. Only trace amounts were present as glycolipids.