Effects of phospholipase A2 treatment of human erythrocyte membranes on the rates of spectrin-actin dissociation

This work examines the extent to which alterations in the composition of the phospholipid bilayer of the erythrocyte membrane influences the stability of the association of the ‘cytoskeletal network’ to the rest of the membrane. Rates of spectrin-actin dissociation at low ionic strength were used as a measure of the stability, and composition of the phospholipid bilayer was altered by the action of the enzyme phospholipase A₂. Hydrolysis of all the phosphatidylcholine of the outer leaflet of the bilayer had no effect on dissociation rates, whether or not the hydrolysis products were extracted with albumin. Hydrolysis of inner leaflet phospholipids increased the rates by up to 2-fold if the hydrolysis products were not extracted; for ?50% hydrolysis, the rates were unaffected if the hydrolysis products were extracted. The moderate magnitudes of the increases in dissociation rates indicate that interactions between the ‘cytoskeletal network’ and the phospholipid bilayer are not a decisive factor in maintaining the stability of the membrane, at least under low ionic strength conditions.