Research

The roles of GPI-anchors in host-parasite interactions

The Project Leader's Profile

Taroh Kinoshita

Vice Director and Professor, Laboratory of Immunoglycobiology, WPI Immunology Frontier Research Center, and Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University

Taroh Kinoshita graduated from the University of Tokyo in 1974, and in 1981 obtained Ph.D. from Osaka University Medical School where he was appointed Research Associate in the Department of Bacteriology in 1982.  From 1982 to 1985 he resided in the Department of Pathology, New York University School of Medicine, as a Research Associate and in 1988 as Assistant Professor at the Department of Bacteriology, Osaka University Medical School.  In 1990 he was named Professor of the Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, where in 2001 received the Osaka Science Award.  From 2003 to 2007 he was Director of the Research Institute for Microbial Diseases, Osaka University. Since 2007, he holds the position of Vice Director and Professor of Immunoglycobiology at WPI Immunology Frontier Research Center.

Project Leader
  • Taroh Kinoshita, Ph.D., Professor, Laboratory of Immunoglycobiology, WPI Immunology Frontier Research Center, and Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University
Research Members
  • Yusuke Maeda, M.D., Ph.D., Associate Professor, Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University
  • Yoshiko Murakami, M.D., Ph.D., Associate Professor, Research Institute for Microbial Diseases, Osaka University
  • Yasuhiro Morita, Ph.D., Assistant Professor, Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University
  • Morihisa Fujita, Ph.D., Assistant Professor for Global COE Program, Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University
Research Collaborators
  • Yetao Wang, M.D., Ph.D., Post-doctoral Fellow, Laboratory of Immunoglycobiology, WPI Immunology Frontier Research Center, Osaka University
  • Noriyuki Kanzawa, Ph.D., Post-doctoral Fellow, Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University
  • Matthew Stokes, Ph.D., Post-doctoral Fellow, Laboratory of Immunoglycobiology, WPI Immunology Frontier Research Center, Osaka University
  • Takeshi Fukuda, Ph.D., Post-doctoral Fellow, Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University

Summary

We have these major projects, "GPI" as a Key Word.

1) GPI-anchor biosynthesis and transport/remodeling of GPI-anchored proteins (GPI-APs)
GPI (glycosylphosphatidylinositol)-anchor is a glycolipid that acts as a lipid anchor for various plasma-membrane proteins. GPI-APs play important roles in the host's self-defense, signal transduction, and other important processes. PIG (Phosphatidyl Inositol Glycan) genes are involved in the biosynthesis of GPI-anchor and the binding to proteins in the ER. PGAP (Post GPI-attachment to Proteins) genes are involved in later processes, lipid remodeling of GPI-anchor, which enables GPI-APs to be localized on the rafts. In the mutants defective in lipid remodeling, GPI-APs cannot be localized on the rafts. Now, we try to isolate novel mutant cell lines defective in transport of GPI-APs, and investigate further on the biological meaning of GPI in the organelle networks using these mutants.

2) Pathogenesis of PNH (Paroxysmal nocturnal hemoglobinuria)
PNH is an acquired hematopoietic stem cell disorder in which clonal cells defective in GPI biosynthesis are expanded. Abnormal erythrocytes lack CD59 and DAF/CD55, widely distributed GPI anchored proteins that inhibit activation of complement on the host cell surface, are very sensitive to complement and are lysed during infections and other events. We have reported that the responsible gene is PIG-A, the catalytic subunit of the first enzyme in GPI biosynthesis. We are proposing 3step model. Step 1 involves the generation of a GPI-deficient hematopoietic stem cell by somatic mutation in the PIG-A gene. Step 2 involves the immunological selection of GPI-deficient hematopoietic stem cells. At this step, GPI-deficient cells survive and proliferate much more frequently than usual to compensate for anemia. Elevated proliferation would increase the chance of additional genetic mutations. Step 3 involves the generation of a subclone bearing the growth phenotype. We are to identify the cytotoxic cells and their targets, a GPI-AP which plays a role in immunological selection and an additional genetic mutation.

3) Glycolipid biosynthesis in pathogens and its application to drug development
Our particular interest is the biosynthesis of GPIs in Trypanosoma brucei and mycobacteria. Trypanosoma brucei is the causative agent of African sleeping sickness while mycobacteria cause a number of diseases including tuberculosis. These glycolipids are located to the cell surface of these pathogens, and appear to play key roles in evasion from the host's immune attack. We consider the biosynthesis of these glycolipids as potential drug targets, and take multilateral approaches with primary focus on the comprehensive understanding of the GPI biosynthesis at molecular levels.

4) The roles of pH homeostasis in Golgi apparatus
The organelles along secretory pathway such as Golgi apparatus possess proper acidic pHs that are critical for their functions, but the mechanisms by which acidic pHs regulate their functions are largely unknown. We established mutant cells defective in acidification of the Golgi, analyzed the abnormal phenotypes, identified GPHR responsible for the defects and clarified its function. The aim of our project is to resolve the physiological roles of acidic pH homeostasis in the Golgi, in terms of glycosylation, protein trafficking and signaling, using GPHR knockout cells and mice. In addition, we are trying to identify new factors involved in protein trafficking between the ER and Golgi using new mutant cells established by new methods to monitor protein trafficking.

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Some of Recent Papers

  1. Maeda Y, Ide T, Koike M, Uchiyama Y, and Kinoshita T. GPHR is a novel anion channel critical for acidification and functions of the Golgi apparatus. Nat. Cell Biol., 10:1135-1145, 2008.
  2. Maeda Y, Tashima Y, Houjou T, Fujita M, Yoko-o T, Jigami Y, Taguchi R, and Kinoshita T. Fatty Acid Remodeling of GPI-anchored Proteins Is Required for Their Raft Association. Mol. Biol. Cell, 18:1497-1506, 2007.
  3. Morita YS, Sena CB, Waller RF, Kurokawa K, Sernee MF, Nakatani F, Haites RE, Billman-Jacobe H, McConville MJ, Maeda Y, Kinoshita T. PimE is a polyprenol-phosphate-mannose-dependent mannosyltransferase that transfers the fifth mannose of phosphatidylinositol mannoside in mycobacteria. J. Biol. Chem., 281:25143-55, 2006.
  4. Almeida AM*, Murakami Y*, Layton DM, Hillmen P, Sellick GS, Maeda Y, Richards S, Patterson S, Kotsianidis I, Mollica L, Crawford DH, Baker A, Ferguson M, Roberts I, Houlston R, Kinoshita T, Karadimitris A. Hypomorphic promoter mutation in PIGM causes inherited glycosylphosphatidylinositol deficiency. Nat. Med., 12:846-851, 2006. (*equally contributed)
  5. Inoue N, Izui-Sarumaru T, Murakami Y, Endo Y, Nishimura JI, Kurokawa K, Kuwayama M, Shime H, Machii T, Kanakura Y, Meyers G, Wittwer C, Chen Z, Babcock W, Frei-Lahr D, Parker CJ, Kinoshita T. Molecular basis of clonal expansion of hematopoiesis in two patients with paroxysmal nocturnal hemoglobinuria (PNH). Blood, 108:4232-6, 2006.