Identification of a functional role for lipid asymmetry in biological membranes: Phosphatidylserine-skeletal protein interactions modulate membrane stability

Abstract

Asymmetric distribution of phospholipids is ubiquitous in the plasma membranes of many eukaryotic cells. The majority of the aminophospholipids are located in the inner leaflet whereas the cholinephospholipids are localized predominantly in the outer leaflet. Several functional roles for asymmetric phospholipid distribution in plasma membranes have been suggested. Disruption of lipid asymmetry creates a procoagulant surface on platelets and serves as a trigger for macrophage recognition of apoptotic cells. Furthermore, the dynamic process of phospholipid translocation regulates important cellular events such as membrane budding and endocytosis. In the present study, we used the red cell membrane as the model system to explore the contribution of phospholipid asymmetry to the maintenance of membrane mechanical properties. We prepared two different types of membranes in terms of their phospholipid distribution, one in which phospholipids were scrambled and the other in which the asymmetric distribution of phospholipids was maintained and quantitated their mechanical properties. We documented that maintenance of asymmetric distribution of phospholipids resulted in improved membrane mechanical stability. The greater difficulty in extracting the spectrinactin complex at low-ionic strength from the membranes with asymmetric phospholipid distribution further suggested the involvement of interactions between aminophospholipids in the inner leaflet and skeletal proteins in modulating mechanical stability of the red cell membrane. These findings have enabled us to document a functional role of lipid asymmetry in regulating membrane material properties.A symmetric distribution of phospholipids is ubiquitous in the plasma membranes of many eukaryotic cells. The majority of the aminophospholipids, phosphatidylserine (PS) and phosphatidylethanolamine (PE), are located in the inner leaflet whereas the cholinephospholipids, phosphatidylcholine and sphingomyelin, are localized predominantly in the outer leaflet (1, 2). At least three distinct activities are involved in the regulation of membrane lipid sidedness. The MgATPdependent aminophospholipid translocase, (also known as flippase or ATPase II; ref. 3), is responsible for localization of PS and PE in the inner leaflet by rapidly translocating them from the outer to inner leaflet against the electrochemical gradient (4-6). PS is a better substrate than PE for the aminophospholipid translocase (7-9), and the stoichiometry between aminophospholipid translocation and ATP hydrolysis is close to one (10). The activity of the aminophospholipid translocase is inhibited by high concentrations of Ca 2ϩ (11)(12)(13), by the pseudosubstrates of P-type ATPase such as vanadate (14), acetyl phosphate, and p-nitrophenyl phosphate (15), and by sulfhydryl reactive reagents such as N-ethylmaleimide (16) and pyridyldithioethylamine (PDA), a specific inhibitor of phospholipid translocase (16)(17)(18)(19). The less specific MgATP-requiring phospholipid translocase, floppase, moves phospholipids f...

A Rostrocaudal Muscular Dystrophy Caused by a Defect in Choline Kinase Beta, the First Enzyme in Phosphatidylcholine Biosynthesis

“…The active movement of phospholipids between membrane bilayers is a relatively rapid process, and a loss of asymmetry can lead to disruptions in signal transduction pathways (58) along with alterations in membrane stability (59). Apoptosis is initiated by a redistribution of phospholipids in the membrane, specifically with phosphatidylserine relocalizing to the outer leaflet where it can be recognized by macrophages.…”

Platelet Microvesicles (Microparticles) in Cardiac Surgery

“…13 A rise in cytosolic calcium following platelet activation has a key role in the production of PMV through its action on these enzymes (Figure 2). Flippase and aminophospholipid translocase are inhibited, disabling them from holding phosphatidylserine (PS) and phosphatidylethanolamine on the inner membrane layer, 14 while activation of floppases and lipid scramblase causes rapid outward translocation of PS and loss of membrane asymmetry.…”

The Rim101 Pathway Is Involved in Rsb1 Expression Induced by Altered Lipid Asymmetry

“…For instance, in mammals skeletal proteins like spectrin improve the mechanical stability of red blood cells by interacting with PS in the inner leaflet (Manno et al, 2002). Similarly, when certain glycerophospholipid translocase genes (DNF1, DNF2, DNF3, and DRS2) are deleted in yeast, intracellular trafficking and maintenance of organelle structure are impaired (Chen et al, 1999;Gall et al, 2002;Hua et al, 2002;Pomorski et al, 2003;Natarajan et al, 2004;Saito et al, 2004;Furuta et al, 2007).…”