Juntendo University, Tokyo, established in 1838.

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  4. Kazuhisa Iwabuchi, PhD

Institute for Environmental and Gender-Specific Medicine

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Kazuhisa Iwabuchi, PhD

  • Professor, Laboratory for Biochemistry, Juntendo University School of Health Care and Nursing
  • Associate Professor, Institute for Environmental and Gender-specific Medicine, Juntendo University Graduate School of Medicine

Group members:

Fumiko Yoshizaki PhD. Postdoctoral fellow
Hitoshi Nakayama Graduate student (Environmental and Gender-specific Medicine)
Junko Tomiyama Graduate student (Environmental and Gender-specific Medicine)
Chihiro Iwahara Research Assistant
Yoshiyuki Matsushige Research Assistant

Research Speciality:

We will focus on glycosphingolipid-supramolecular domains-mediated functions in innate immunity.

Research Description:

Molecular mechanisms of Innate Immunity

Research interest:

Project 1:
Study of structure and signal transduction mechanisms of glycosphingolipid-supramolecular domains involved in adhesion, migration and phagocytosis of leukocytes
   Glycosphingolipids are membrane components consisting of hydrophobic ceramide and hydrophilic sugar moieties. They cluster to form glycosphingolipid-enriched supramolecular domains (or so called microdomains / lipid rafts) on cellular membrane. Biochemical analyses have demonstrated that glycosphingolipid-enriched microdomains contain several kinds of transducer molecules, especially membrane-anchored signal transduction molecules such as Src family kinases. Although it has been speculated that glycosphingolipids are closely associated with cell differentiation, proliferation and functions such as adhesion, there are quite few evidence that glycosphingolipids by themselves directly mediate signal transductions, which lead to cell functions. Glycosignaling domains (GSDs) have been identified as glycosphingolipid-mediated signal transduction units in mouse melanoma B 16 cells, mouse neuroblastoma Neuro2a cells and human neutrophils (Fig. 1). In those cells, certain kinds of glycosphingolipids, e.g. LacCer for neutrophils, are highly expressed on cell surfaces, and associated with Src family kinases in GSD. We know that Lyn molecules bind to cytoplasmic leaflet. However, LacCer is not located in the cytoplasmic leaflet of membrane bilayer. So how does LacCer interact with signal transducer molecules? To elucidate this question, we analyzed the molecular species of microdomain components using proteomics and lipidemics analysis.

Project 2:
Molecular dynamics of escape mechanisms of mycobacterium from neutrophil killing
   Pathogenic Mycobacterium species such as M. avium, and M. tuberculosis are responsible for a wide variety of human ailments. In phagocytes, Mycobacteriums inhibit the fusion between lysosomal granules and their phagosomes, leading to the proposal that these properties favor their survival in phagocytes. Neutrophils have been also demonstrated to phagocytose Mycobacteriums without fusion of lysosomes (Azurophil granules) with phagosomes. Although neutrophils play a defensive role during mycobacterial infections, mobilization of granules in response to Mycobacteria has not been well characterized. LacCer is binders for several kinds of microorganisms. Moreover, it has been demonstrated that lipid rafts (microdomains) play some roles in penetration of Mycobacteriums. To elucidate molecules controlling the process of mobilization/fusion of these granules with the phagosomal or the plasma membrane in neutrophils, we observed LacCer localization during phagocytosis of Mycobacteriums.

Project 3:
Evaluation of the effect of exogenous endocrine disrupting chemicals on innate immune system
"Exogenous endocrine disrupting chemicals" have been identified as "Exogenous substances which interfere with the normal function of hormones when taken into the body." It has been pointed out recently by many researchers and experts that some chemicals in the environment may impair the immune system of human. This is an important potential problem for environmental protection. We focus on the molecular mechanisms of immune modulatory effect of environmental chemical compounds in innate immunity.

Fig. 1 LacCer-enriched GSD
Neutrophils recognize microorganisms such as bacteria and fungi through LacCer. On plasma membrane of neutrophils, LacCer forms microdomains so called glycosingnaling domains coupled with a Src family tyrosine kinase Lyn. When specific ligands such as β-glucan bind to LacCer in GSD, GSD gather to form big clusters with Lyn, leading to superoxide generation through PI3K-, p38 MAPK-, and protein kinase C-dependent signal transduction pathway.

Publication list:

  1. Takaya N, Katoh Y, Iwabuchi K, Hayashi I, Konishi H, Itoh S, Okumura K, Ra C, Nagaoka I, Daida H: Platelets activated by collagen through the immunoreceptor tyrosine-based activation motif in the Fc receptor gamma-chain play a pivotal role in the development of myocardial ischemia-reperfusion injury. J Mol Cell Cardiol. Published in on line Oct 21; 2005
  2. Kaga N, Kazuno S, Taka H, Iwabuchi K, and Murayama K.: Isolation and characterization of molecular species of lactosylceramides derived from HL-60 and porcine blood cells using liquid chromatography/electrospray ion trap mass spectrometry. Anal. Biochem. 337, 316-24, 2005
  3. Kashiwakura Y, Tamayose K, Iwabuchi K, Hirai Y, ShimadaT, MatsumotoK, Nakamura T, Watanabe M, Oshimi K, Daida H.: HGF receptor is a coreceptor for adeno-associated virus type 2 (AAV2) infection. J. Virology 79: 609-14, 2005
  4. Iwabuchi K.: Structure and functions of glycosignaling domain. TIGG 17, 1-14 (2005)
  5. Hua J., Suguro S., Iwabuchi K., Tsutsumi-Ishii Y., Sakamoto K., Nagaoka I.: Glucosamine, a naturally ccurring amino monosaccharide suppresses the ADP-mediated platelet activation in humans. Inflammation Res. 53, 680-8, 2004
  6. Sato S, Ishii K, Makino A, Iwabuchi K, Yamaji-Hasegawa A, Senoh Y, Nagaoka I, Sakuraba H, Kobayashi T. Distribution and transport of cholesterol-rich membrane domains monitored by a membrane-impermeant fluorescent poly (ethylene glycol)-derivatized cholesterol. J.Biol.Chem. 279, 23790-6, 2004
  7. Hamaguchi A, Suzuki H, Murayama K, Fujimura T, Hikita T, Iwabuchi K, Handa K, Withers DA, Masters SC, Fu H, Hakomori S.: Sphingosine-dependent protein kinase-1 (SDK-1) is identified as the kinase domain of PKCδ. J. Biol Chem. 278:41557-65, 2003
  8. Hamaguchi A, Suzuki E, Murayama K, Fujimura T, Hikita T, Iwabuchi K, Handa K, Withers DA, Masters SC, Fu H, Hakomori S.: A sphingosine-dependent protein kinase that specifically phosphorylates 14-3-3 (SDK1) is identified as the kinase domain of PKC delta: a preliminary note. Biochem Biophys Res Commun. 307:589-94, 2003
  9. Ohwada A, Tsutsumi-Ishii Y, Yoshioka Y, Iwabuchi K, Nagaoka I, Fukuchi Y.: Acid exposure potentiates ICAM-1 and E-cadherin expression on A549 alveolar lining epithelial cells. Experimental Lung Research, 29:389-400, 2003
  10. Ohwada A, Yoshioka Y, Iwabuchi K, Nagaoka I, Dambara T, Fukuchi Y: VEGF regulates the proliferation of acid-exposed alveolar lining epithelial cells. Thorax in press Thorax 58:328-32, 2003
  11. Niyonsaba F, Iwabuchi K, Someya A, Hirata M, Matsuda M, Ogawa H, Nagaoka I: A cathelicidin family of human antibacterial peptide LL-37 induces mast cells chemotaxis. Immunology 106: 20-26, 2002
  12. Iwabuchi K, Nagaoka I: Lactosylceramide-enriched glycosphingolipid signaling domain mediates superoxide generation from human neutrophils. Blood 100:1454-1464, 2002
  13. Niyonsaba F, Iwabuchi K, Matsuda H, Ogawa H, Nagaoka I: Epithelial cell-derived human β-defensin-2 acts as chemotaxin for mast cells through pertussis toxin-sensitive and phospholipase C-dependent pathway. Int Immunol 14: 421-426, 2002
  14. Maekawa H, Iwabuchi K, Nagaoka I, Watanabe H, Kamano T, Tsurumaru M: Activated peritoneal macrophages inhibit the proliferation of rat ascites hepatoma AH-130 cells via the production of tumor necrosis factor-alpha and nitric oxide. Inflamm Res 49: 541-547, 2000
  15. Iwabuchi K, Zhang Y, Nunomura S, Hakomori S: Effect of synthetic sialyl 2-->1 sphingosine and other glycosylsphingosines on the structure and function of the "glycosphingolipid signaling domain (GSD)" in mouse melanoma B16 cells. Biochemistry 39:2459-2468, 2000 (First two authors are equally contributed)
  16. Iwabuchi K, Zhang Y, Handa K, Withers DA, Sinay P, Hakomori S: Reconstitution of membranes stimulating "glycosignaling domain" and their susceptibility to lyso-GM3. J Biol Chem 275:15174-15181, 2000
  17. Iwabuchi K, Handa K, Hakomori S: Separation of glycosphingolipid-enriched microdomain from caveolae characterized by presence of caveolin. In: Methods in Enzymology: Sphingolipid Metabolism and Cell Signaling. Hannun YA and Merrill, Jr.AH eds 1999, 488-494, Academic Press, San Diego, 2000
  18. Megidish T, Hamaguchi A, Iwabuchi K, Hakomori S: Assays of sphingosine-dependent kinase (SDK1) for 14-3-3 protein. In: Methods in Enzymology: Sphingolipid Metabolism and Cell Signaling. Hannun YA and Merrill, Jr.AH eds 1999, 381-387, Academic Press, San Diego, 2000
 Introduction
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