Combined Program on Microbiology and Immunology. Osaka University.

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Research Theme :
The roles of GPI-anchors in host-parasite interactions

Principal Research Scientist
Taroh Kinoshita
Profile:

1970 – 1977 Master of Agriculture, University of Tokyo, Graduate School of
Agriculture
1977 –1981 Ph.D., Osaka University, Graduate School of Medicine
1981 – 1982 Post-Doctoral Research Fellow, Japan Society for Promotion of Science
1982 –1988 Research Associate, Department of Bacteriology, Osaka University,
School of Medicine [Research theme] Biology of Complement
1982 –1985 Visiting Research Associate, New York University, School of Medicine [Research theme] Medical biology of complement controlling factors
1987 Visiting Research Associate, Basel Institute of Immunology (Switzerland) [Research theme] Biochemistry of complement controlling factors
1988 – 1990 Assistant Professor, Department of Bacteriology, Osaka University, School of Medicine [Research theme] Biology of complement receptors
1990 – present Professor, Research Institute for Microbial Diseases, Osaka University
[Research theme] Biology and Medicine of GPI anchored proteins
1998 – 2003 Director of the Genome Information Research Center, Osaka University
October 2003 – present Director, Research Institute for Microbial Diseases, Osaka University

1993 –1995 Principal Investigator on Grant-in-Aid for Specially Promoted Research, "Cloning of GPI anchor biosynthesis gene PIG-A and elucidation of its clinical significance"
1997 –1983 Collaborator on COE project, Osaka University, "Molecular biology and medicine of infectious disease and immune disease"
1996 –1998 Principal Investigator for Human Frontier Science Program, "Post-translational modification by a GPI anchor in host and parasite"

Collaborators

Yusuke Maeda, Kisaburo Nagamune, Yoshiko Murakami
(Department of Immunoregulation, Research institute for Microbial Diseases)

Yasuhiro Morita (Research Associate of COE)

Research Summary

GPI anchors consist of glycolipids, which have been identified in a wide range of organisms from archaebacteria to eukaryotes, and are known to be involved in binding numerous proteins to the cell surface. GPI anchors play important roles on both the parasite side and the host side during the course of infection. In protozoa, most major membrane proteins are GPI anchors, which are likely to play an important role in interaction with the host. Our research has been directed towards Trypanosoma brucei, a causative agent of African sleeping sickness (Human African Trypanosomiasis), and we have demonstrated that a GPI anchor is a potential target for the development of a trypanocidal agent. In this project, we intend to thoroughly analyze and compare the biosynthetic pathways of GPI anchored proteins both in trypanosomes and the host, in order to discover a drug(s) that is able to selectively inhibit biosynthesis of trypanosome GPI anchors. Although typical GPI anchors have not yet been found in prokaryotes, the acid-fast bacteria are known to contain GPI-like glycolipids; thus, we will also include these bacteria in our current study.
On the other hand, in host cells, intracellular signal transduction originates at GPI anchor type proteins on the cell membrane; these GPI anchor proteins are concentrated in the microdomain, or so-called "raft", and act as a portal of entry for pathogens. It is this "raft" where the GPI anchor proteins trigger signal transduction and become a site for attachment of viral receptors and bacteria to the host cell. Genomic analysis of the PIG (Phosphatidyl Inositol Glycan) gene cluster, which encodes proteins involved in GPI biosynthesis and post-translational transfer to proteins in the endocytoplasmic reticulum (ER), is currently underway and 80-90% complete. In this project, we aim to analyze the PGAP (Post Attachment of GPI-anchor) gene cluster, which encodes proteins involved in the process whereby GPI anchor proteins are transferred from the ER and concentrated at the raft.

We have determined the structure of the subunits of enzyme required for GPI anchor attachment in Trypanosoma brucei. As a result of a comparison study with human enzyme for GPI anchor attachment, we have identified two novel and essential subunits, TTA1 and TTA2, which exist only in Trypanosoma. As GPI anchors are essential for the survival of bloodborne Trypanosoma brucei (virulent type), drugs inhibiting the function of TTA1 or TTA2 may have trypanocidal activity without affecting host enzymes. Thus, these subunits are promising targets for therapeutic treatment of sleeping sickness, a serious issue in African countries, and also nagana disease, which is a fatal threat for livestock in Africa. Our future objectives include a comparison study for the entire GPI anchor pathway to determine differences in the mechanisms of Trypanosoma and human GPI anchors.

A GPI anchor is synthesized in the ER, and ligated to target proteins. We have been studying the PIG gene cluster (Phosphatidyl Inositol Glycan) which encodes proteins involved in the process whereby GPI is anchored to proteins. To date, we have completed the sequencing of 23 genes. GPI anchor precursors are synthesized in the ER, are transported to the cell surface while their side chains are modified, and are then concentrated within the raft. We aim to characterize PGAP gene clusters (Post GPI-anchor Attachment to Proteins), which encode proteins involved in these processes, is underway.

Publications

1. Nagamune, K., T. Nozaki, Y. Maeda, K. Ohishi, T. Fukuma, T. Hara, R. T. Schwarz, C.
Sutterlin, R. Brun, H. Riezman and T. Kinoshita. 2000. Critical roles of glycosylphosphatidylinositol for Trypanosoma brucei. Proc. Natl. Acad. Sci. USA 97:10336-10341.

2. Ohishi, K., N. Inoue and T. Kinoshita. 2001. PIG-S and PIG-T, essential for GPI-anchor
attachment to proteins, form a complex with GAA1 and GPI8. EMBO J. 20:4088-4098.

3. Hong, Y., K. Ohishi, N. Inoue, J. Y. Kang, H. Shime, Y. Horiguchi, F. G. van der Goot, N.
Sugimoto and T. Kinoshita. 2002. Requirement of N-glycan on GPI-anchored proteins for efficient binding of aerolysin but not Clostridium septicum ?-toxin. EMBO J. 21:5047-5056.

4. Murakami, Y., H. Kosaka, Y. Maeda, J. Nishimura, N. Inoue, K. Ohishi, M. Okabe, J.
Takeda and T. Kinoshita. 2002. Inefficient response of T lymphocytes to glycosylphosphatidylinositol-negative cells: implications for paroxysmal nocturnal hemoglobinuria. Blood 100:4116-4122.

5. Nagamune, K., K. Ohishi, H. Ashida, Y. Hong, J. Hino, K. Kangawa, N. Inoue, Y. Maeda
and T. Kinoshita. 2003. GPI transamidase of Trypanosoma brucei has two novel (TTA1 and TTA2) and three common subunits. Proc. Natl. Acad. Sci. USA 100:10682-10687.