title: Transbilayer distribution of lipids at nano scale.
abstract: There is a limited number of methods to examine transbilayer lipid distribution in biomembranes. We employed freeze-fracture replica-labelling immunoelectron microscopy in combination with lipid-binding proteins and a peptide to examine both transbilayer distribution and lateral distribution of various phospholipids in mammalian cells. Our results indicate that phospholipids are exclusively distributed either in the outer or inner leaflet of human red blood cell (RBC) membranes. In contrast, in nucleated cells, such as human skin fibroblasts and neutrophils, sphingomyelin was distributed in both leaflets while exhibiting characteristic lipid domains in the inner leaflet. Similar to RBCs, lipid asymmetry was maintained both in resting and thrombin-activated platelets. However, the microparticles released from thrombin-activated platelets lost membrane asymmetry. Our results suggest that the microparticles were shed from platelet plasma membrane domains enriched with phosphatidylserine and/or phosphatidylinositol at the outer leaflet. These findings underscore the strict regulation and cell-type specificity of lipid asymmetry in the plasma membrane.
authors: Lipid Biology Laboratory, RIKEN, Wako, Saitama 351-0198, Japan.
authors: Motohide
authors: M
authors: Murate
authors: Lipid Biology Laboratory, RIKEN, Wako, Saitama 351-0198, Japan.
authors: Mitsuhiro
authors: M
authors: Abe
authors: Laboratory of Biomembrane, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan.
authors: Kohji
authors: K
authors: Kasahara
authors: Laboratory for Biochemistry, Institute for Environmental and Gender-specific Medicine, Juntendo University Graduate School of Medicine, Urayasu, Chiba 279-0021, Japan.
authors: Kazuhisa
authors: K
authors: Iwabuchi
authors: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.
authors: Masato
authors: M
authors: Umeda
authors: Lipid Biology Laboratory, RIKEN, Wako, Saitama 351-0198, Japan Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 1060, Université Lyon 1, Villeurbanne 69621, France kobayasi@riken.jp.
authors: Toshihide
authors: T
authors: Kobayashi
mesh_terms: D001792:Blood Platelets / Q000166:cytology*; D002462:Cell Membrane / Q000737:chemistry*; D004912:Erythrocytes / Q000166:cytology*; D005347:Fibroblasts / Q000166:cytology*; D006367:HeLa Cells; D006801:Humans; D009504:Neutrophils / Q000166:cytology; D010718:Phosphatidylserines / Q000737:chemistry*
chemical_list: D010718:Phosphatidylserines
keywords: Electron microscopy; Freeze fracture; Lipid asymmetry; Microdomain; Plasma membrane