The lipid head group is the key element for substrate recognition by the P4 ATPase ALA2: a phosphatidylserine flippase.

Type IV P-type ATPases (P4 ATPases) are lipid flippases that catalyze phospholipid transport from the exoplasmic to the cytoplasmic leaflet of cellular membranes, but the mechanism by which they recognize and transport phospholipids through the lipid bilayer remains unknown. In the present study, we succeeded in purifying recombinant aminophospholipid ATPase 2 (ALA2), a member of the P4 ATPase subfamily in , in complex with the ALA-interacting subunit 5 (ALIS5). The ATP hydrolytic activity of the ALA2-ALIS5 complex was stimulated in a highly specific manner by phosphatidylserine.

Monitoring dynamic spiculation in red blood cells with scanning ion conductance microscopy.

Phospholipids are critical structural components of the membrane of human erythrocytes and their asymmetric transbilayer distribution is essential for normal cell functions. Phospholipid asymmetry is maintained by transporters that shuttle phospholipids between the inner leaflet and the outer leaflet of the membrane bilayer. When an exogenous, short acyl chain, phosphatidylcholine (PC) or phosphatidylserine (PS) is incorporated into erythrocytes, a discocyte-to-echinocyte shape change is induced.

Enhanced vascular function after acute fat-rich snacking in healthy males.

Diets high in fat are associated with vascular dysfunction. Frequent snacking may exacerbate this problem by extending the postprandial state. We hypothesized that repeated fat-rich mixed snacks would impair peripheral endothelial function and increase oxidative stress, a purported causal factor.

The yeast plasma membrane ATP binding cassette (ABC) transporter Aus1: purification, characterization, and the effect of lipids on its activity.

The ATP binding cassette (ABC) transporter Aus1 is expressed under anaerobic growth conditions at the plasma membrane of the yeast Saccharomyces cerevisiae and is required for sterol uptake. These observations suggest that Aus1 promotes the translocation of sterols across membranes, but the precise transport mechanism has yet to be identified. In this study, an extraction and purification procedure was developed to characterize the Aus1 transporter.

Regulation of phospholipid asymmetry in the erythrocyte membrane.

Purpose Of Review: Alterations in the transbilayer distribution of phospholipids in the erythrocyte membrane have significant physiologic consequences. Understanding the cause of these perturbations and the molecular mechanisms by which they are regulated is essential for ameliorating some of the consequences of erythrocyte membrane abnormalities. This review summarizes recent data that provide a clearer description of the molecular events involved in these processes.

ATP-dependent transport of phosphatidylserine analogues in human erythrocytes.

The plasma membrane of most cells contains a number of lipid transporters that catalyze the ATP-dependent movement of phospholipids across the membrane and assist in the maintenance of lipid asymmetry. The most well-characterized of these transporters is the erythrocyte aminophospholipid flippase, which selectively transports phosphatidylserine (PS) from the outer to the inner monolayer. Previous work has demonstrated that PS and to a lesser extent phosphatidylethanolamine (PE) are substrates for the flippase and that other phospholipids move across the membrane only by passive flip-flop.

Lipid specific activation of the murine P4-ATPase Atp8a1 (ATPase II).

The asymmetric transbilayer distribution of phosphatidylserine (PS) in the mammalian plasma membrane and secretory vesicles is maintained, in part, by an ATP-dependent transporter. This aminophospholipid "flippase" selectively transports PS to the cytosolic leaflet of the bilayer and is sensitive to vanadate, Ca(2+), and modification by sulfhydryl reagents. Although the flippase has not been positively identified, a subfamily of P-type ATPases has been proposed to function as transporters of amphipaths, including PS and other phospholipids.

The role of oxidative stress in diabetic complications.

The morbidity and mortality associated with diabetes is the result of the myriad complications related to the disease. One of the most explored hypotheses to explain the onset of complications is a hyperglycemia-induced increase in oxidative stress. Reactive oxygen species (ROS) are produced by oxidative phosphorylation, nicotinamide adenine dinucleotide phosphate oxidase (NADPH), xanthine oxidase, the uncoupling of lipoxygenases, cytochrome P450 monooxygenases, and glucose autoxidation.

Interaction between phosphatidylserine and the phosphatidylserine receptor inhibits immune responses in vivo.

Phosphatidylserine (PS) on apoptotic cells promotes their uptake and induces anti-inflammatory responses in phagocytes, including TGF-beta release. Little is known regarding the effects of PS on adaptive immune responses. We therefore investigated the effects of PS-containing liposomes on immune responses in mice in vivo.

Regulation of transbilayer plasma membrane phospholipid asymmetry.

Lipids in biological membranes are asymmetrically distributed across the bilayer; the amine-containing phospholipids are enriched on the cytoplasmic surface of the plasma membrane, while the choline-containing and sphingolipids are enriched on the outer surface. The maintenance of transbilayer lipid asymmetry is essential for normal membrane function, and disruption of this asymmetry is associated with cell activation or pathologic conditions. Lipid asymmetry is generated primarily by selective synthesis of lipids on one side of the membrane.