Aminophospholipid translocase of human erythrocytes: phospholipid substrate specificity and effect of cholesterol

Abstract

The outside-inside translocation rate and transmembrane equilibrium distribution, at 37 degrees C, of 16 different amphiphilic spin-labeled phospholipids have been determined in human erythrocytes. The transmembrane distribution was assessed by bovine serum albumin extraction of the spin-labels present in the outer monolayer. Within 15 min, more than 90% of the phosphatidylserine analogue was found in the inner monolayer; the equilibrium distribution of phosphatidylethanolamine spin-label was approximately 85-90% inside, with a half-time for translocation of approximately 50 min. In contrast, phosphatidylcholine reached a distribution corresponding to approximately 30% of the labels inside with a half-time of approximately 8 h, and only traces of sphingomyelin were found in the inner monolayer after 16 h. Thus, the spin-label analogues distributed themselves like endogenous phospholipids in red cells with a spontaneous segregation between the amino lipids and the choline-containing phospholipids. Progressive methylation of the amine group of phosphatidylethanolamine resulted in a stepwise decrease of the specific transport; modification of the beta-carbon of the serine also decreased the efficiency of the rapid translocation without abolishing it. Phosphatidyl-propanolamine was not transported. Substitution of the glyceride group by a ceramide abolished the rapid outside-inside translocation even with a molecule bearing a serine head group. Also it was found that esterification of the sn-2 position of the glycerol component was necessary for a rapid translocation since lysophosphatidylserine was only slowly transported from outside to inside.(ABSTRACT TRUNCATED AT 250 WORDS)

Partial purification and characterization of the human erythrocyte Mg2+ ‐ATPase A candidate aminophospholipid translocase

“…On the other hand, PE allowed the protein to express some activity. This remarkably specific lipid specificity expressed by the Mg2+-ATPase parallels the substrate specificity of the aminophospholipid translocase [2,16]: the enzyme transports PS and PE, but the apparent affinity of PS is one order of magnitude higher than that of PE. Besides, lyso PS is not a good substrate and is transported very inefficiently, and PC is not recognized at all by the carrier.…”

“…The human erythrocyte membrane and other plasma membranes contain an aminophospholipid translocase which actively transports phosphatidylserine (PS) and phosphatidylethanolamine (PE) from the outer to the inner monolayer [1,2]. This transport requires the hydrolysis of cytosolic ATP [1,3,4], the presence of magnesium [5] and is inhibited by vanadate [1,5]; it is therefore a vanadate sensitive Mg-ATPase.…”

Lysolipids Do Not Inhibit Influenza Virus Fusion by Interaction with Hemagglutinin

“…Thus, all SL-LPC were extracted from liposomes and bound to BSA. It has been previously shown that BSA can extract those analogs from the exposed outer leaflet but not from the inner leaflet (35).…”

Oxidative stress and phosphatidylserine exposure in red cells from patients with sickle cell anaemia

“…Myeloperoxidase released from activated neutrophils may also add to oxidant challenge in SCA, through production of hypochlorous acid (HOCl) from hydrogen peroxide (Vissers et al , 1994; Mutze et al , 2003; Zhang et al , 2013). Thiol oxidation has also been associated with both inhibition of the flippase and stimulation of the scramblase (Morrot et al , 1989; Connor & Schroit, 1990; Devaux & Zachowski, 1994; Martin & Jesty, 1995; de Jong & Kuypers, 2006). In addition, the normal antioxidant capacity of the red cell is compromised in SCA patients, with low availability of antioxidant enzymes, reduced levels of glutathione (GSH) and also of non‐enzymatic antioxidants, such as vitamins C and E (Silva et al , 2013).…”