Erythrocyte phospholipid organization and vesiculation in hereditary high red cell membrane phosphatidylcholine hemolytic anemia

Abstract

We have studied the erythrocyte membrane phospholipid organization in hereditary high red cell membrane phosphatidylcholine hemolytic anemia (HPCHA) and the response of these red cells during incubation with sonicated suspensions of dimyristoylphosphatidylcholine (DMPC). Although both the absolute and relative amounts of phosphatidylcholine were elevated in these red cells, the relative distribution of phosphatidylcholine on both sides of the membrane bilayer and the transbilayer mobility of phosphatidylcholine were normal. HPCHA erythrocytes showed elevated absolute amounts per cell of both protein and lipid and an increased cellular ratio of protein to phospholipid. Incubation of normal red cells with DMPC led to the formation of echinocytes, followed by the release of acetylcholinesterase-containing vesicles. Both echinocyte formation and vesiculation were markedly reduced in red cells from patients with HPCHA. Studies with red cells from patients with liver disease, cells that also have elevated relative amounts of membrane phosphatidylcholine and increased amounts of lipid per cell, revealed normal echinocyte formation and normal DMPC-induced vesiculation. We conclude that the altered lipid composition of HPCHA erythrocytes per se is not responsible for the observed reduction in DMPC-induced vesiculation, but that it is more likely the result of a modification in the protein moiety of these cells. This putative protein abnormality could enhance binding of phosphatidylcholine to red cell membranes and could explain the elevated phosphatidylcholine content of HPCHA erythrocytes and their inability to vesiculate.