Complete exchange of phosphatidylcholine from intact erythrocytes after protein crosslinking

Treatment of human erythrocytes with tetrathionate or diamide resulted in extensive crosslinking of membraneous and cytoskeletal proteins. Such treatment was followed by an incubation with phosphatidylcholine specific exchange protein to investigate the rate and extent of exchange of phosphatidylcholine between the erythrocytes and ¹⁴C-labeled phosphatidylcholine containing microsomal membranes or vesicles. Exchange profiles showed that the exchange of phosphatidylcholine is facilitated in treated cells when compared to control erythrocytes and, more importantly, that all of the phosphatidylcholine is exchangeable after protein crosslinking whereas in control cells only the phosphatidylcholine pool located in the outer layer of the membrane is exchangeable. These observations demonstrate that crosslinking of cytoskeletal and membraneous proteins enhances the rate of transbilayer movement of phosphatidylcholine considerably.