Akiko Yamaji-Hasegawa

RIKEN, Вако, Saitama, Japan

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Publications (9)29.97 Total impact

  • Akiko Yamaji-Hasegawa, Masafumi Tsujimoto
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    ABSTRACT: In eukaryotic cells, the biological membrane is characterized by a non-uniform distribution of membrane lipids, vertically as well as laterally. The paradigm for the vertical non-random distribution is the plasma membrane, where phosphatidylcholine (PC), sphingomyelin (SM), and glycosphingolipids are primarily located on the exoplasmic leaflet, while aminophospholipids, including phosphatidylserine (PS) and phosphatidylethanolamine (PE), are generally enriched in the cytoplasmic leaflet. Other minor phospholipids, such as phosphatidic acid and phosphatidylinositol (PI), are also enriched on the cytoplasmic face. Such asymmetrical distribution is related to each lipid regulating various biological events through interaction with other molecules. The clarification of the regulatory mechanism of the distribution and movement of membrane lipids is crucial to understanding the physiological roles of lipids. Here we focus on PS, which has been reported to be involved in apoptosis, blood coagulation and other biological phenomena, and summarize the present understanding of the dynamics of this phospholipid, including biosynthesis, metabolism, transport, and transbilayer movement. We also refer to diseases that have been reported to be related to phospholipid asymmetry.
    Biological & Pharmaceutical Bulletin 09/2006; 29(8):1547-53. · 1.85 Impact Factor
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    ABSTRACT: Sphingolipids and their metabolites are known to modulate various cellular events including proliferation, differentiation, and apoptosis. Serine palmitoyltransferase (SPT) is the enzyme that catalyzes the first step of the biosynthesis of all sphingolipids. Here, we report that a newly identified antibiotic, sulfamisterin, derived from the fungus Pycnidiella sp., is a specific inhibitor of SPT. The chemical structure of sulfamisterin resembles both that of sphingosine as well as a potent inhibitor of SPT, ISP-1 (myriocin). Sulfamisterin inhibited SPT activity with IC(50) = 3 nM in a cell-free lysate prepared from Chinese hamster ovary (CHO) fibroblasts. Sulfamisterin markedly inhibited the biosynthesis of sphingolipids in living CHO cells and in yeast Saccharomyces cerevisiae as monitored by radioactive precursors. Unlike the cell-free experiments, 10 microM sulfamisterin was required for complete inhibition of sphingolipid biosynthesis in intact cells. We also synthesized a series of structural analogues of sulfamisterin and examined their activities both in cell-free and in living cell systems.
    Biochemistry 02/2005; 44(1):268-77. · 3.38 Impact Factor
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    ABSTRACT: The first total synthesis of (+)-sulfamisterin (AB5366), a naturally occurring alpha-substituted alpha-amino acid derivative possessing a sulfonated hydroxy function, is described. Overman rearrangement of an allylic trichloroacetimidate derived from D-tartrate effectively generated the tetrasubstituted carbon containing a nitrogen substituent. Construction of the amino acid moiety and sulfonation of the hydroxy group, followed by deprotection completed the total synthesis, which fully confirmed the proposed absolute structure of the natural product. The possible stereoisomers of (+)-sulfamisterin and their desulfonated derivatives were also synthesized. Biological assessment of all synthetic compounds revealed that natural (+)-sulfamisterin and its 3-epimer as well as their desulfonated derivatives possessing 2S-configuration strongly inhibit the serine palmitoyl transferase both in vitro and in vivo, whereas compounds with 2R-configuration were found to show much weaker inhibitory activity.
    The Journal of Antibiotics 02/2005; 58(1):37-49. · 2.19 Impact Factor
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    ABSTRACT: Lysenin is a sphingomyelin (SM)-specific toxin isolated from the coelomic fluid of the earthworm Eisenia foetida. Lysenin comprises a family of proteins together with lysenin-related protein 1 (LRP-1, lysenin 2) and LRP-2 (lysenin 3). In the present study, we characterized LRP-1 and LRP-2 together with lysenin using maltose-binding-protein-tagged recombinant proteins. LRP-2 specifically bound SM and induced hemolysis like lysenin. In contrast the binding and hemolytic activities of LRP-1 were 10 times less than those of lysenin and LRP-2. Lysenin and LRP-2 share 30 common sites of aromatic amino acids. Among them, only one position, phenylalanine 210, is substituted for isoleucine in LRP-1. The activity of LRP-1 was dramatically increased by introducing a single amino acid substitution of isoleucine 210 to phenylalanine, suggesting the importance of this aromatic amino acid in biological activities of lysenin and LRPs. The importance of aromatic amino acids was further indicated by a systematic tryptophan to alanine mutation of lysenin. Lysenin contains six tryptophan residues of which five are conserved in LRP-1 and -2. We showed that the conserved tryptophans but not the nonconserved one were required both in the recognition of SM and in the hemolytic activity of lysenin. Our results suggest the importance of tryptophan in the toxin function likely due to a direct recognition of SM or in maintaining the protein structure.
    Biochemistry 09/2004; 43(30):9766-73. · 3.38 Impact Factor
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    ABSTRACT: Cholesterol-rich membrane domains function in various membrane events as diverse as signal transduction and membrane traffic. We studied the interaction of a fluorescein ester of polyethylene glycol-derivatized cholesterol (fPEG-Chol) with cholesterol-rich membranes both in cells and in model membranes. Unlike filipin and other cholesterol probes, this molecule could be applied as an aqueous dispersion to various samples. When added to live cells, fPEG-Chol distributed exclusively in the outer plasma membrane leaflet and was enriched in microdomains that dynamically clustered by the activation of receptor signaling. The surface-bound fPEG-Chol was slowly internalized via clathrin-independent pathway into endosomes together with lipid raft markers. Noteworthy, fPEG-Chol could be microinjected in the living cells in which we found Golgi apparatus as the sole major organelle to be labeled. PEG-Chol, thus, provides a novel, sensitive probe for unraveling the dynamics of cholesterol-rich microdomains in living cells.
    Journal of Biological Chemistry 06/2004; 279(22):23790-6. · 4.65 Impact Factor
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    ABSTRACT: Little is known about the heterogenous organization of lipids in biological membranes. Sphingomyelin (SM) is a major plasma membrane lipid that forms lipid domains together with cholesterol and glycolipids. Using SM-specific toxin, lysenin, we showed that in cultured epithelial cells the accessibility of the toxin to SM is different between apical and basolateral membranes. Apical membranes are highly enriched with glycolipids. The inhibitory role of glycolipids in the binding of lysenin to SM was confirmed by comparing the glycolipid-deficient mutant melanoma cell line with its parent cell. Model membrane experiments indicated that glycolipid altered the local density of SM so that the affinity of the lipid for lysenin was decreased. Our results indicate that lysenin recognizes the heterogenous organization of SM in biomembranes and that the organization of SM differs between different cell types and between different membrane domains within the same cell. Isothermal titration calorimetry suggests that lysenin binding to SM is presumably the result of a SM-lysenin complex formation of specific stoichiometry, thus supporting the idea of the existence of small condensed lipid complexes consisting of just a few lipid molecules in living cells.
    Biophysical Journal 02/2004; 86(1 Pt 1):296-307. · 3.67 Impact Factor
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    ABSTRACT: Lysenin is a novel protein derived from coelomic fluid of the earthworm Eisenia foetida, which specifically recognizes sphingomyelin and induces cytolysis. The mechanism underlying lysenin-induced cell lysis has not been clarified. In this report we studied the interaction of lysenin with red blood cells as well as artificial liposomes. Our results showed that lysenin bound membranes and assembled to SDS-resistant oligomers in a sphingomyelin-dependent manner, leading to the formation of pores with a hydrodynamic diameter of approximately 3 nm. Antibody scanning analysis suggested that the C-terminal region of lysenin was exposed, whereas the N-terminal was hidden in the isolated oligomer complex. Differential scanning calorimetry revealed that lysenin interacted with both hydrophilic head group and hydrophobic hydrocarbon tails of sphingomyelin. Oligomerization but not binding was affected by the amide-linked fatty acid composition of sphingomyelin, suggesting the role of membrane fluidity in the oligomerization step.
    Journal of Biological Chemistry 07/2003; 278(25):22762-70. · 4.65 Impact Factor
  • Akiko Yamaji-Hasegawa, Toshihide Kobayashi
    Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme 04/2002; 47(4 Suppl):519-25.
  • T Kobayashi, A Yamaji-Hasegawa, E Kiyokawa
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    ABSTRACT: Whereas endosomes connect with both exocytic and endocytic organelle via extensive lipid and protein traffic, each endosome has a distinct lipid and protein composition. Recent observations suggest that different lipid membrane domains exist even in the same endosome. These lipid domains, together with low pH milieu, may present a variety of micro-environments to cargo molecules. Evidence is accumulating which suggests that the alteration of these lipid microdomains may be involved in a number of pathological conditions.
    Seminars in Cell and Developmental Biology 05/2001; 12(2):173-82. · 6.20 Impact Factor