© 2004 The Japanese Biochemical Society
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Degradation of Fodrin by m-Calpain in Fibroblasts Adhering to Fibrillar Collagen I Gel
1 Department of Molecular Biology, Tokyo Metropolitan Institute of Medical Science, 3-18-22 Honkomagome, Bunkyo-ku, Tokyo 113-8613; 2 Nippi Research Institute of Biomatrix and Institute of Leather Research, Nippi Co., Ltd., Tokyo 112-8601; 3 Department of Enzymatic Regulation for Cell Functions, Tokyo Metropolitan Institute of Medical Science, Tokyo 113-8613; and 4 Department of Protein Biochemistry, Tokyo Metropolitan Institute of Gerontology, Tokyo 173-0015,
When skin fibroblasts were cultured on fibrillar collagen I gel, we observed rapid degradation of talin, fodrin and ezrin, which are well-known calpain substrates. The protease m-calpain was activated only in cells adhering to fibrillar collagen, whereas µ-calpain was activated in cells adhering to monomeric or fibrillar collagen at the same level. The calpain inhibitor Z-Leu-Leu-aldehyde inhibited degradation of fodrin, but not talin. Degradation of fodrin, 
-actinin and ezrin was prevented by over-expression of dominant negative m-calpain. However, over-expression of calpastatin, an endogenous calpain inhibitor, had no effect the degradation of these three proteins. These results suggest that m-calpain is responsible for degradation of their membrane proteins via adhesion to fibrillar collagen I gel.
* To whom correspondence should be addressed at the present address: The present address is Department of Matrix Biology, Kennedy Institute of Rheumatology, Faculty of Medicine, Imperial College London. 1 Aspenlea Road, Hammersmith, London W6 8LH, UK, Fax: +44 (0)20-8383-4499, E-mail: ksq{at}mac.com