ATP-dependent redistribution of phosphatidylethanolamine in the plasma membrane of an epithelial and a hepatocytic cell line.

The redistribution of spin-labeled phospholipid analogues of sphingomyelin (SM) and phosphatidylethanolamine (PE) from the outer to the inner leaflet of the plasma membrane of an epithelial (CaCo-2) and a hepatocytic cell line (HepG2) was investigated. The amount of analogues in the outer leaflet was determined by their back-exchange to bovine serum albumin (BSA). For both cell lines a fast ATP-dependent inward movement of spinlabeled PE (SL-PE) was found while SL-SM redistributed only slowly by a passive mechanism. After depletion of intracellular ATP transverse diffusion of SL-PE was similar to that of SL-SM. The data are compatible with the presence of an aminophospholipid translocase in both cell lines.