Erythrocytes attached to a wheat germ agglutinin coated surface display an altered phospholipid metabolism

Erythrocytes were bound to a lectin-coated surface; the multivalent attachment to this surface resulted in a severe deformation of the cells and an alteration in the cellular phospholipid metabolism. Human erythrocytes were allowed to bind for 20 min at 20 degrees C to polystyrene beads coated with wheat germ agglutinin (WGA beads). The bound erythrocytes were then lysed to produce stroma bound to WGA beads. Control stroma and stroma-WGA beads were incubated at 37 degrees C with gamma-32P-ATP to examine the phospholipid labeling patterns. The control stroma incorporated 32P-label into phosphatidylinositol-4-phosphate and phosphatidylinositol-4,5-bisphosphate, in agreement with earlier studies. However, the stroma-WGA beads showed incorporation of 32P-label into phosphatidic acid in addition to that in the phosphoinositides. The quantity of 32P-phosphatidic acid produced during the 20-min assay was 3.23 +/- 0.84 (n = 7) picomoles/micrograms stromal cholesterol; the amount synthesized, however, was dependent on the procedure used to prepare the stroma-WGA beads. If the erythrocytes were bound to the WGA beads at 0 degrees C instead of 20 degrees C, the quantity of 32P-phosphatidic acid produced during the subsequent 37 degrees C assay with gamma-32P-ATP was decreased 4.2 fold; the phosphoinositide labeling pattern was unchanged. In addition, when the time for binding of intact erythrocytes to the WGA beads was varied from 1 to 20 minutes, there was a time-dependent increase in the amount of 32P-phosphatidic acid produced. This induction of phosphatidic acid synthesis could not be duplicated with fluid phase WGA. Therefore, the multivalent binding of intact erythrocytes to WGA beads causes an alteration in phospholipid metabolism.