Mobility modulation by local concanavalin A binding. Selectivity toward different membrane proteins

We have employed fluorescence photobleaching recovery to demonstrate selective immobilization of lymphocyte membrane proteins by localized concanavalin A (ConA) binding to the cell surface. Localized ConA binding was achieved by the binding of ConA coupled to paraformaldehyde-fixed platelets to mouse spleen lymphocytes. The effect of the localized cross-linking of ConA receptors on the lateral mobility of specific membrane proteins at regions distal to the ConA platelets was investigated. The diffusion of surface immunoglobulins and ConA receptors was inhibited above a threshold coverage (12%) of the upper lymphocyte surface by ConA platelets. In contrast, no effect was observed on the diffusion and aggregation of mouse histocompatibility antigens (H-2K(k)) labeled with a fluorescent monoclonal antibody. Since the ConA modulation was shown to propagate through the cytoskeleton, these results indicate specificity in the interactions of membrane proteins with the cytoskeleton. This specificity enables a selective response of different membrane proteins to the ConA anchorage modulation.