Transmembrane mobility and distribution of phospholipids in the membrane of mouse β-thalassaemic red blood cells

Abstract

Using spin-labelled lipid analogues, the transmembrane mobility and distribution of phospholipids in normal and β-thalassaemic murine red blood cells were investigated. The velocities of spin-labelled phosphatidylserine (PS∗) and spin-labelled phosphatidylethanolamine (PE∗) active transport into the inner leaflet were not significantly different between normal and pathological cells. The stationary distribution of PE∗ in thalassaemic erythrocytes ( 79.5 ± 2.0% inside ) differed from that of control cells ( 91.1 ± 1.6% inside ), while that of PS∗ was unaffected. In thalassaemic cells the passive diffusion of spin-labelled phosphatidylcholine (PC∗) was accelerated 4-fold and its stationary distribution was shifted to 34.5 ± 2.3% inside compared to 19.5 ± 1.6% in control cells. Spin-labelled sphingomyelin (SM∗), which showed no inward movement in normal cells, diffused partially towards the inner leaflet of thalassaemic erythrocyte membranes. These results indicate that modifications of the transverse lipid organisation in β-thalassaemic red blood cells are due to changes in passive diffusion movements, and not to changes in aminophospholipid translocase activity.