Restriction of receptor mobility and the agglutination of cells by concanavalin a

Abstract

Summary Transformed hamster fibroblasts with a high ATP content which are not agglutinated by concanavalin A (ConA) can be induced to agglutinate by decreasing their ATP content, mixing of glutaraldehyde prefixed ConA-coated cells with unfixed uncoated cells, or mixing of unfixed ConA-saturated cells with uncoated cells. The decrease in ATP content required for a gain of ConA agglutination between unfixed cells, was associated with a decrease in the short range rapid lateral mobility (RLM) of ConA surface receptors and with an increased exposure of the surface membrane phospholipids. The transformed fibroblasts with a high ATP content were agglutinated by the lectin from wheat germ (WGA) and after neuraminidase treatment also by the lectin from soybean (SBA). Agglutination by these two lectins was not effected by changes in the cellular ATP content. The half maximum rate ( V m ) of ConA-induced agglutination of cells with a low ATP content required 75% saturation of the cell receptors for ConA and was temperature sensitive. The half V m of agglutination between prefixed ConA-coated and unfixed uncoated cells, like the WGA- and SBA-induced agglutination of unfixed cells, required only about 15% saturation and was less temperature sensitive. The results indicate, that in cells with a high RLM of ConA receptors, agglutination induced by ConA required an appropriate degree of restriction of receptor mobility to allow the alignment of surface receptors that is required for agglutination. This restriction can be obtained by lowering the ATP content, mixing of prefixed lectin coated cells with unfixed uncoated cells, or saturating unfixed cells with ConA before mixing with unfixed uncoated cells. The results also suggest that the receptors for ConA are differently embedded in the lipid phase of the surface membrane than the receptors for WGA and SBA.