Adhesion of Dictyostelium discoideum cells to carbohydrates immobilized in polyacrylamide gels. I. Evidence for three sugar-specific cell surface receptors.

Dictyostelium discoideum cells appear to be able to recognize particular carbohydrate prosthetic groups at different stages in their life cycle. We therefore used our previously developed model system (consisting of polyacrylamide gels containing putative ligands covalently linked to the polymer) to determine the receptors on these cells capable of recognizing carbohydrates. D. discoideum cells, at different developmental stages from growth phase to late aggregation, were incubated with the derivatized gels, and the number of adherent cells was determined by measuring alanine transaminase after cell lysis. From 70 to 100% of the cells firmly adhered to gels derivatized with glucose, maltose, or cellobiose. The cells were also capable of binding to N-acetylglucosamine and mannose, but both the rate and the extent of binding to these sugars were less than those observed with the glucose derivatives. Furthermore, binding to N-acetylglucosamine decreased to negligible levels during the aggregation stage of development. The cells did not bind to the glucose-derivatized gels in the presence of glucose and a variety of carbohydrates containing glucose at the nonreducing termini, whereas binding was not inhibited by N-acetylglucosamine, mannose, and derivatives of these sugars. Adhesion to all sugars was blocked by 2,4-dinitrophenol. This inhibitor also reversed the binding to gels containing N-acetylglucosamine and mannose, but not to glucose. Differential binding to the three monosaccharides was also observed under conditions affecting the normal amoeboid shape of the cells. In addition, adhesion to N-acetylglucosamine and mannose was trypsin-sensitive, whereas adhesion to glucose was only slightly affected by treating the cells with trypsin (and cycloheximide). These and other results suggest that D. discoideum cell adhesion to derivatized gels is mediated by three different receptors, one highly specific for glucose and two (probably less specific) for N-acetylglucosamine and mannose.