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Department of Biochemistry

Outline

In 1945, Professor Yashiro Kotake, the first President of the school at that time, started this department. Since then, Professors Yahito Kotake, Kazuo Hotta, Katashi Ichihara, Yuichi Matsumura, Ryo Kido, and Morimitsu Nishikimi successively served as the chairman of the department, and Professor Yoshito Ihara has been the chairman since 2007.

Educational Outline

We teach courses in the following educational programs.

  1. Biochemistry and Metabolism (for 2nd grade students of the School of Medicine)
  2. Molecular Cellular Biology (for 2nd grade students of the School of Medicine)
  3. Metabolism in the Cell (for students of the Graduate School of Medicine)

Research Outline

Our work is focused on clarifying the molecular mechanisms involved in the post-translational regulation of glycoproteins in the cell, and the roles in cell biology, physiology and pathology. We have two main research topics, which concern [1] C-mannosyl tryptophan, a unique post-translational modification in cellular proteins, and [2] calreticulin, a lectin chaperone regulating quality control of glycoprotein biosynthesis and Ca2+ homeostasis in the endoplasmic reticulum.

[1] Protein C-mannosylation is unique in that an a・mannose attaches directly to the indole C2 carbon atom of a tryptophan residue through a C-C bond. C-Mannosylation usually occurs at the first tryptophan in the consensus amino acid sequence Trp-x-x-Trp (W-x-x-W) through an enzymatic reaction with a specific mannosyltransferase, which has yet to be identified. Most substrates for C-mannosylation are part of either the thrombospondin type-1 repeat (TSR) superfamily or cytokine receptor family, suggesting a functional role for C-mannosylation in specific substrates. Site-directed mutagenesis in the W-x-x-W motif has revealed C-mannosylation to be important in the folding or targeting of substrate proteins, such as mucins and ADAMTS-like 1, in the cell. Furthermore, we identified Hsc70 as a protein specifically bound to C-mannosylated TSR-derived peptides, and found that the interaction of Hsc70 with C-mannosylated peptides enhanced the TNF-a・producing signaling by Hsc70 in macrophage-like cells. These findings suggest that the C-mannosylation of some target proteins plays pivotal functional roles in the cell. We examine the role of C-mannosylation in proteins using molecular biological, biochemical, immunological and biophysical techniques.

Our research goal is to clarify the molecular mechanism of protein C-mannosylation and its physiological or pathological functions in the cell.

Selected References

  1. C-Mannosylation: a modification on tryptophan in cellular proteins.: Ihara Y., Inai Y., Ikezaki M., Matsui I.-L., Manabe S., and Ito Y. In “Glycoscience: Biology and Medicine” (Eds.) Taniguchi N., Endo T., Hart G.W., Seeberger P., and Wong C.-H., Springer-Verlag GmbH, Heidelberg, Germany, 1091-1099, 2014.
  2. Protein C-mannosylation and its prospective functions in the cell.: Ihara Y., Inai Y., and Ikezaki M. Trends Glycosci. Glycotechnol., 23, 1-13, 2011.
  3. C-Mannosylated peptides derived from the thrombospondin type 1 repeat interact with Hsc70 to modulate its signaling in RAW264.7 cells.: Ihara Y., Manabe S., Ikezaki M., Inai Y., Matsui I.-S. L., Ohta Y., Muroi E., and Ito Y. Glycobiology, 20, 1298-1310, 2010.
  4. C-Mannosylated peptides derived from the thrombospondin type 1 repeat enhance lipopolysaccharide-induced signaling in macrophage-like RAW264.7 cells.: Muroi E., Manabe S., Ikezaki M., Urata Y., Sato S., Kondo T., Ito Y., and Ihara Y. Glycobiology, 17, 1015-1028, 2007.

[2] Calreticulin is a Ca2+-binding multifunctional molecular chaperone in the endoplasmic reticulum. Calreticulin is involved in a variety of cellular processes including the quality control of glycoprotein synthesis in the endoplasmic reticulum, Ca2+ homeostasis, intracellular signaling, gene expression, and nuclear transport. In cancer cells, the altered expression of calreticulin may lead to alterations in cellular characteristics, such as growth, adhesion, motility, immune responses, and susceptibility to apoptosis.

Previously, we reported that overexpression of calreticulin through gene transfection caused epithelial-mesenchymal transition (EMT)-like changes in epithelia-derived Madin-Darby Canine Kidney cells. The EMT is a crucial process controlling the morphogenesis of multicellular organisms during embryogenesis, development, and disease states such as malignancies, chronic inflammation, and tissue fibrosis. In the study, we found that overexpression of calreticulin repressed E-cadherin gene expression through up-regulation of its repressor, Slug, via altered Ca2+ homeostasis. These results suggested a novel function of calreticulin related to EMT-like changes of cellular phenotype. We examine the role of calreticulin in the EMT machinery using molecular biological, biochemical, immunological and biophysical techniques.

Our research goal is to clarify the unrevealed mechanism of calreticulin-induced EMT and its physiological or pathological relevance to cellular functions.

Selected References

  1. Epithelial calreticulin up-regulation promotes profibrotic responses and tubulointerstitial fibrosis development.: Prakoura N., Politis P.K., Ihara Y., Michalak M., and Charonis A.S. Am. J. Pathol., 183, 1474-1487, 2013.
  2. Alteration of integrin-dependent adhesion and signaling in EMT-like MDCK cells established through overexpression of calreticulin.: Ihara Y., Inai Y., and Ikezaki M. J. Cell. Biochem., 112, 2518-2528, 2011.
  3. Calreticulin represses E-cadherin gene expression in MDCK cells via slug.: Hayashida Y., Urata Y., Muroi E., Kono T., Miyata Y., Nomata K., Kanetake H., Kondo T., and Ihara Y. J. Biol. Chem., 281, 32469-32484, 2006.
  4. Calreticulin, a molecular chaperone in the endoplasmic reticulum, modulates radiosensitivity of human glioblastoma U251MG cells.: Okunaga T., Urata Y., Goto S., Matsuo T., Mizota S., Tsutsumi K., Nagata I., Kondo T., and Ihara Y. Cancer Res., 66, 8662-8671, 2006.

Contact

Yoshito Ihara, Professor
Department of Biochemistry, Wakayama Medical University School of Medicine,
811-1 Kimiidera, Wakayama 641-8509, Japan.
Phone/Fax: 81-73-441-0628
E-mail: y-ihara(at)wakayama-med.ac.jp