HOME > Members > GCOE Organizing Members > Toyoshi Fujimoto MD, PhD

Toyoshi Fujimoto MD, PhDProfessor, Department of Molecular Cell Biology, Nagoya University Graduate School of Medicine

Specialized field

Anatomy and Cell Biology

Career Summary

March, 1978
Graduated from Kyoto University Faculty of Medicine
April, 1978
Assistant Professor, Department of Anatomy Kyoto University Faculty of Medicine
February, 1982
Associate Professor, Department of Anatomy
Kyoto University Faculty of Medicine
May, 1995
Professor and Chairman
Department of Anatomy and Cell Biology
Gunma University School of Medicine
April, 1999-present
Professor and Chairman
Department of Anatomy and Molecular Cell Biology
Nagoya University Graduate School of Medicine

Research Theme

Nano-scale analysis of lipid-based structures

Research Summary

Nano-scale analysis of lipid-based structures

Research Purpose and Results:
[1] Apolipoprotein B-100 (ApoB) is the principal component of very low density lipoprotein. Poorly lipidated nascent ApoB is extracted from the Sec61 translocon and degraded by proteasomes. ApoB lipidated in the endoplasmic reticulum (ER) lumen is also subjected to proteasomal degradation, but where and how it dislocates to the cytoplasm remain unknown. In the present study, we demonstrate that ApoB after lipidation is dislocated to the cytoplasmic surface of lipid droplets (LDs) and accumulates as ubiquitinated ApoB in Huh7 cells. Depletion of UBXD8, which is almost confined to LDs in this cell type, decreases recruitment of p97 to LDs and causes an increase of both ubiquitinated ApoB on the LD surface and lipidated ApoB in the ER lumen. In contrast, abrogation of Derlin-1 function induces an accumulation of lipidated ApoB in the ER lumen but does not increase ubiquitinated ApoB on the LD surface. UBXD8 and Derlin-1 bind with each other and with lipidated ApoB and show colocalization around LDs. These results indicate that ApoB after lipidation is dislocated from the ER lumen to the LD surface for proteasomal degradation and that Derlin-1 and UBXD8 are engaged in the predislocation and postdislocation steps, respectively.
[2] Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is a phospholipid that has been implicated in multiple cellular activities. The distribution of PI(4,5)P2 has been analyzed extensively using live imaging of the GFP-coupled phospholipase C-δ1 pleckstrin homology domain in cultured cell lines. However, technical difficulties have prevented the study of PI(4,5)P2 in cells of in vivo tissues. We recently developed a method to analyze the nanoscale distribution of PI(4,5)P2 in cultured cells by using the quick-freezing and freeze-fracture replica labeling method. In principle, this method can be applied to any cell because it does not require the expression of artificial probes. In the present study, we modified the method to study cells of in vivo tissues and applied it to pancreatic exocrine acinar cells of the rat. We found that PI(4,5)P2 in the plasma membrane is distributed in an equivalent density in the apical and basolateral domains, but exists in a significantly higher concentration in the gap junction. The intracellular organelles did not show labeling for PI(4,5)P2. The results are novel or different from the reported distribution patterns in cell lines and highlight the importance of studying cells differentiated in vivo.

Principal Research Achievement

  1. Fujimoto T, Fukazawa Y. Electron microscopy of membrane lipids. In Encyclopedia of Biophysics, Roberts G, ed. (Berlin, Springer-Verlag), p. in press (2012)
  2. Suzuki M, Shinohara Y, Fujimoto T: Histochemical detection of lipid droplets in cultured cells. Methods Mol Biol, in press (2012)
  3. Suzuki M, Otsuka T, Ohsaki Y, Cheng J, Taniguchi T, Hashimoto H, Taniguchi H, Fujimoto T: Derlin-1 and UBXD8 are engaged in dislocation and degradation of lipidated ApoB-100 at lipid droplets. Mol Biol Cell, 23, 800-810 (2012)
  4. Suzuki M, Shinohara Y, Ohsaki Y, Fujimoto T: Lipid droplets: size matters. J Electron Microsc (Tokyo), 60 Suppl 1, S101-116 (2011)
  5. Kawai Y, Hamazaki Y, Fujita H, Fujita A, Sato T, Furuse M, Fujimoto T, Jetten AM, Agata Y, Minato N: Claudin-4 induction by E-protein activity in later stages of CD4/8 double-positive thymocytes to increase positive selection efficiency. Proc Natl Acad Sci U S A, 108, 4075-4080 (2011)
  6. Ozato-Sakurai N, Fujita A, Fujimoto T: The distribution of phosphatidylinositol 4,5-bisphosphate in acinar cells of rat pancreas revealed with the freeze-fracture replica labeling method. PLoS One, 6, e23567 (2011)
  7. Fujimoto T, Parton RG: Not just fat: the structure and function of the lipid droplet. Cold Spring Harb Perspect Biol, 3 (2011)
  8. Hishiki T, Shimizu Y, Tobita R, Sugiyama K, Ogawa K, Funami K, Ohsaki Y, Fujimoto T, Takaku H, Wakita T, Baumert TF, Miyanari Y, Shimotohno K: Infectivity of hepatitis C virus is influenced by association with apolipoprotein E isoforms. J Virol, 84, 12048-12057 (2010)
  9. Ohsaki Y, Suzuki M, Shinohara Y, Fujimoto T: Lysosomal accumulation of mTOR is enhanced by rapamycin. Histochem Cell Biol, 134, 537-544 (2010)
  10. Shimizu Y, Hishiki T, Sugiyama K, Ogawa K, Funami K, Kato A, Ohsaki Y, Fujimoto T, Takaku H, Shimotohno K: Lipoprotein lipase and hepatic triglyceride lipase reduce the infectivity of hepatitis C virus (HCV) through their catalytic activities on HCV-associated lipoproteins. Virology, 407, 152-159 (2010)
  11. Fujita A, Fujimoto, T. Nanoscale Analysis of Glycolipid Distribution in the Cell Membrane. Trends Glycosci Glycotech, 126, 173-181 (2010)
  12. Fujita A, Cheng J, Fujimoto T. Quantitative electron microscopy for the nanoscale analysis of membrane lipid distribution. Nature Protocols, 5, 661-669 (2010)
  13. Ohsaki S, Shinohara Y, Suzuki M, Fujimoto T, A pitfall in using BODIPY dyes for lipid droplet labeling. Histochem Cell Biol, 133, 477-480 (2010)
  14. Fujita A, Fujimoto T. High Resolution Molecular Localization by Freeze-Fracture Replica Labeling, Schwartzbach SD, Osafune T (eds.), Immuno-electron Microscopy. Methods Mol Biol, 657, 205-216 (2010)
  15. Fujita A, Cheng J, Tauchi-Sato K, Takenawa T, Fujimoto T. A distinct pool of phosphatidyl- inositol 4,5-bisphosphate in caveolae revealed by a nanoscale labeling technique. Proc Natl Acad Sci USA, 106, 9256-9261 (2009)
  16. Fujita A, Cheng J, Fujimoto T. Segregation of GM1 and GM3 clusters in the cell membrane depends on the intact actin cytoskeleton. Biochim Biophys Acta, 1791, 388-396 (2009)
  17. Cheng J, Fujita A, Ohsaki Y, Suzuki M, Shinohara Y, Fujimoto T. Quantitative electron microscopy shows uniform incorporation of triglycerides into existing lipid droplets. Histochem Cell Biol, 132, 281-291 (2009)
  18. Ohsaki Y, Cheng J, Suzuki M, Shinohara Y, Fujita A, Fujimoto T. Biogenesis of cytoplasmic lipid droplets: from the lipid ester globule in the membrane to the visible structure. Biochim Biophys Acta, 1791, 399-407 (2009)
  19. Ohsaki Y, Cheng J, Suzuki M, Fujita A, Fujimoto T. Lipid droplets are arrested in the ER membrane by tight binding of lipidated apolipoprotein B-100. J Cell Sci, 121, 2415-2422 (2008)
  20. Nishino N, Tamori Y, Tateya S, Kawaguchi T, Shibakusa T, Mizunoya W, Inoue K, Kitazawa R, Kitazawa S, Matsuki Y, Hiramatsu R, Masubuchi S, Omachi A, Kimura K, Saito M, Amo T, Ohta S, Yamaguchi T, Osumi T, Cheng J, Fujimoto T, Nakao H, Nakao K, Aiba A, Okamura H, Fushiki T, Kasuga M. FSP27 contributes to efficient energy storage in murine white adipocytes by promoting the formation of unilocular lipid droplets. J Clin Invest, 118, 2808-2821 (2008)
  21. Urahama Y, Ohsaki Y, Fujita Y, Maruyama S, Yuzawa Y, Matsuo S, Fujimoto T. Lipid droplet-associated proteins protect renal tubular cells from fatty acid-induced apoptosis. Am J Pathol, 173, 1286-1294 (2008)
  22. Kurahashi M, Niwa Y, Cheng J, Ohsaki Y, Fujita A, Goto, H, Fujimoto T, Torihashi S. Platelet-derived growth factor signals play critical roles in differentiation of longitudinal smooth muscle cells in mouse embryonic gut. Neurogastroenterol Motil, 20, 521-531 (2008)
  23. Fujimoto T, Ohsaki Y, Cheng J, Suzuki M, Shinohara Y. Lipid droplets: a classic organelle with a new outfit. Histochem Cell Biol, 136, 263-279 (2008)
  24. Fujita A et al. Gangliosides GM1 and GM3 in the living cell membrane form clusters susceptible to cholesterol depletion and chilling. Mol. Biol. Cell 18: 2812-2822 (2007)
  25. Ohsaki Y et al. Cytoplasmic lipid droplets are sites of convergence of proteasomal and autophagic degradation of apolipoprotein B. Mol. Biol. Cell 17: 2674-2683 (2006)
  26. Ozeki S et al. Rab18 localizes to lipid droplets and induces their close apposition to the endoplasmic reticulum-derived membrane. J. Cell Sci. 118: 2601-2611 (2005)
  27. Nomura R et al. Human coronavirus 229E binds to CD13 in raft and enters the cell through caveolae. J. Virol. 78: 8701-8708 (2004)
  28. Kogo H et al. Cell type-specific occurrence of caveolin-1alpha and -1beta in the lung caused by expression of distinct mRNAs. J. Biol. Chem. 279: 25574-25581 (2004)
  29. Tauchi-Sato K et al. The surface of lipid droplets is a phospholipid monolayer with a unique fatty acid composition. J. Biol. Chem. 277: 44507-44512 (2002)
  30. Torihashi S et al. Calcium oscillation linked to pacemaking of interstitial cell of Cajal; requirement of calcium influx and localisation of TRP4 in caveolae. J. Biol. Chem. 277: 19191-19197 (2002)
  31. Fujimoto T et al. Caveolin-2 is targeted to lipid droplets, a new ‘membrane domain’ in the cell. J. Cell Biol. 152: 1079-1085 (2001)
  32. Fujimoto T et al. Isoforms of caveolin-1 and caveolar structure. J. Cell Sci. 113: 3509-3517 (2000)
  33. Nomura R et al. Tyrosine phosphorylated caveolin-1: immunolocalization and molecular characterization. Mol. Biol. Cell 10: 975-986 (1999)
  34. Isshiki M et al. Endothelial Ca2+ waves preferentially originate at specific loci in caveolin-rich cell edges. Proc. Natl. Acad. Sci. USA. 95: 5009-5014 (1998)
  35. Saitou M et al. Occludin-deficient embryonic stem cells can differentiate into polarized epithelial cells bearing well-developed tight junctions. J. Cell Biol. 141: 397-408 (1998)
  36. Yamamoto-Hino M et al. Apical vesicles bearing inositol 1,4,5-trisphosphate receptors in the Ca2+ initiation site of ductal epithelium of submandibular gland. J. Cell Biol. 141: 135-142 (1998)
  37. Fujimoto K et al. Transmembrane phospholipid distribution revealed by freeze-fracture replica labeling. J. Cell Sci. 109: 2453-2460 (1996)
  38. Fujimoto T et al. Inositol 1,4,5-trisphosphate receptor-like protein in plasmalemmal caveolae is linked to actin filaments. J. Cell Sci. 108: 7-15 (1995)
  39. Fujimoto T. Calcium pump of the plasma membrane is localized in caveolae. J. Cell Biol. 120: 1147-1157 (1993)
  40. Fujimoto T et al. Localization of inositol 1,4,5-trisphosphate receptor-like protein in plasmalemmal caveolae. J. Cell Biol. 119: 1507-1513 (1992)
  41. Fujimoto T et al. Fodrin in the human polymorphonuclear leucocyte: redistribution induced by the chemotactic peptide. J. Cell Sci. 96: 477-484 (1990)
  42. Fujimoto T et al. Immunocytochemical studies of endothelial cells in vivo. I. The presence of desmin only, or of desmin plus vimentin, or vimentin only, in the endothelial cells of different capillaries of the adult chicken. J. Cell Biol. 103: 2775-2786 (1986)


1988 Young Investigator Award
(The 8th International Congress on Histochemistry and Cytochemistry)
1996 Seto Award (The Society Award of The Japanese Society for Electron Microscopy)