Lipid and protein composition of exovesicles released from human erythrocytes following treatment with amphiphiles.

Human erythrocytes were treated with different water-soluble amphiphiles (detergents) at sublytic concentrations, whereafter released exovesicles and treated cells were isolated. Lipid analyses showed that exovesicles had a lower cholesterol/phospholipid ratio and a higher phosphatidylserine/phospholipid ratio compared to parent cells. Protein analyses revealed that exovesicles were, relative to their total protein content, depleted in spectrin, actin and band 6 protein and enriched in band 3 protein and acetylcholinesterase. Exovesicles contained all major glycoproteins. By using a radiolabeled amphiphile ([14C]cetyltrimethylammonium bromide) it was shown that the amphiphile/phospholipid ratio was similar in the vesicle membrane and in the parent cell membrane. This indicates that no significant segregation of the intercalated amphiphile between the exovesicle membrane and the parent cell membrane occurs during the vesiculation process. It is suggested that the redistributions of membrane lipids and proteins during the vesiculation process are secondary to the detachment of the cytoskeletal network from the membrane.