Wheat germ agglutinin but not concanavalin A modulates protein kinase C-mediated phosphorylation of red cell skeletal proteins.

Human red blood cells contain protein kinase C (PKC) which acts exclusively on the membrane skeletal proteins band 4.1, band 4.9 and adducin. PKC activity can be stimulated by the addition of the phorbol ester 12-O-tetradecanoyl phorbol 13-acetate to intact cells. Phosphorylation of band 4.1 by PKC in vitro results in a dramatic reduction in band 4.1 binding to spectrin and actin, as well as to the cytoplasmic domain of band 3. Here we show that the lectin wheat germ agglutinin (WGA), which binds to the extracellular domain of glycophorin results in the inhibition of PKC catalyzed phosphorylation of band 4.1, band 4.9 and likely adducin as well. The lectin concanavalin A, which binds to band 3 was without effect. Our results suggest that the binding of WGA to glycophorin results in a major rearrangement of the membrane skeletal network which correlates with reduced phosphorylation of membrane skeletal proteins by PKC.