Division of Life Style Disease
Research Summary
New specific inhibitors for individual cathepsins were developed based on computer-graphic tertiary structures of cathepsins, such as CA-074 for cathepsin B, CLIK-148 for cathepsin L, CLIK-60 for cathepsin S and CLIK-164 for cathepsin K. Using these specific inhibitors, biological and medical significances of lysosomal cysteine proteases are studied on the insights into the roles of cathepsins in antigen processing and presentation. Administration of cathepsin B specific inhibitor suppressed the response to exogenous antigens and induces switching of the T cell responses from Th-2 to Th-1 of CD4+ T cells, thereby down-regulating the production of IgE and IgG1. Administration of cathepsin S inhibitor impairs presentation of autoantigen, a-fodrin, in Sjogren's syndrome and suppressed the Th-1 response and the autoantibody production.
Katunuma et al developed the new detecting method of cysteine protease inhibitors, named "Reverse Zymography". Using this newly developed technology, various new cysteine proteases were found in human secretory fluids, especially disease specific inhibitors were found in human teas with autoimmune-diseases.
New enzyme participating in induction of liver apoptosis is studied at the molecular level. Novel procaspase-3 activating cascade in liver apoptosis mediated by lactoferrin located in lysosomes was demonstrated. In the case of D-galactosamine-induced liver apoptosis, the lysosomal lactoferrin was released into the cytoplasm and procaspase-3 located in cytoplasm was activated to form caspase-3, and resulted in the induction of liver apoptosis. The caspase-3 activity was specifically inhibited by epigallo-catechin gallate, therefore, all apoptosis mediated by caspase-3 should be protected by epigallo-catechin gallate treatment. Since all 13 lines of cultured cancer cells lacked the lysosomal lactoferrin, these cancer cells showed the resistant to D-galactosamine-induced apoptosis.

Selected Papers
1) N. Katunuma, E. Murata, H. Kakegawa, A. Matsui, H. Tsuzuki, H. Tsuge, D. Turk, V. Turk, M. Fukushima, Y. Tada, T. Asao:
Structure based development of novel specific inhibitors for cathepsin L and cathepsin S in vitro and in vivo;
FEBS-Lett, 458, 6-10 (1999)

2) T. Towatari, T. Nikawa, M. Murata, C. Yokoo, M. Tamai, K. Hanada and N. Katunuma:
Novel Epoxysuccinyl Peptides; A Selective Inhibitor of Cathepsin B in Vivo,
FEBS-Lett. 280(2), 311-315 (1991)

3) K. Takio, E. Kominami, N. Wakamatsu, N. Katunuma and K. Titani:
Amino Acid Sequences of Rat Liver Thiol Proteinase Inhibitors,
Biochem. Biophys. Res. Commun. 115(3), 902-908 (1983)

4) E. Kominami, N. Wakamatsu and N. Katunuma:
Purification and Characterization of Thiol Proteinase Inhibitors from Rat Serum and Liver,
J. Biol. Chem. 257(24), 14648-14652 (1982)

5) Towatari T, Kawabata Y, Katunuma N.:
Crystallization and properties of cathepsin B from rat liver.
Eur J Biochem. 102(1), 279-289 (1979)

6) Katunuma N, Huzino A, Tomino I.:
Organ specific control of glutamine metabolism.
Adv Enzyme Regul. 5, 55-69 (1967)